Circuit Test XB - Variable Control Relay Module (VCRM)

NOTE: You should enter this Pinpoint Test only when directed here from Diagnostic Routines

This pinpoint test is intended to diagnose only the following:

Harness circuits: All associated with VCRM
Variable Control Relay Module (VCRM) (12B581)
Powertrain Control Module (PCM) (12A650)

The Variable Control Relay Module (VCRM) is used to perform the following functions: fuel pump control; engine cooling fan control; A/C clutch control; A/C head pressure control; supply VPWR to the EEC-IV system and Powertrain Control Module (PCM). In addition to these functions, the VCRM performs diagnostic checks of its system. Information on any failure that is detected by the VCRM is sent via DCL (DATA+ and DATA- circuits) to the Powertrain Control Module (PCM). This failure information is output as Diagnostic Trouble Codes (DTC) during EEC-IV Self-Test. Each function is described in more detail below.

Fuel Pump Control

The Mark VIII uses a two speed fuel pump control strategy. The fuel pump receives either B(+) voltage (High Speed Fuel Pump), or a voltage less than B(+) (Low Speed Fuel Pump). The vehicle normally runs on the Low Speed Fuel Pump (FP) with the High Speed Fuel Pump (HFP) activated during engine start-up and high load conditions. For low speed pump operation, the PCM grounds the Fuel Pump (FP) circuit. The VCRM receives this request for the low speed pump and activates the fuel pump output driver, sending voltage to the pump through the power-to-pump circuit. The power-to-pump circuit from the VCRM is designed so that the full B(+) voltage will not reach the pump resulting in low speed pump operation. For high speed pump operation, the PCM grounds the FP circuit and also sends a message through DCL that the high speed pump is requested. With the FP circuit grounded, the VCRM activates the fuel pump output driver as in the low speed operation. With the high speed pump requested, the VCRM will also ground its HFP output closing the normally open contacts of the HFP relay. This sends full B(+) voltage to the pump resulting in high speed pump operation.

Engine Cooling Fan Control

The PCM monitors certain engine parameters (ECT sensor, vehicle speed, A/C demand, A/C head pressure, etc.) to determine engine cooling fan needs. The PCM will send the desired fan speed to the VCRM via DCL. The VCRM then adjusts the fan speed according to vehicle battery voltage, and outputs the appropriate voltage through the fan output driver with a pulse width modulated duty cycle.

A/C Head Pressure Control

The VCRM receives the A/C pressure reading from the A/C Head Pressure (ACP) sensor. This information is supplied to the PCM through the DCL and is used to help determine the desired engine cooling fan speed. The PCM also has the ability to turn off A/C (through WAC) if the A/C head pressure has, or could, exceed the safe limits of the system. The A/C Cyclic Pressure Switch is also used to help control A/C pressure.

A/C Clutch Operation

When the A/C demand switch is turned on and the cyclic pressure switch is closed, voltage is supplied to the VCRM (Pin 9) and to the ACCS circuit (Pin 10). The voltage on the ACCS circuit indicates to the PCM that A/C is requested. The PCM will verify that A/C clutch operation is desireable (ex. engine not cranking or over heated, not at WOT, A/C head pressure OK, etc.). If A/C clutch operation is desireable, the PCM will adjust idle speed as necessary and unground the WAC output, which signals to the VCRM that the A/C clutch may be activated. The VCRM will then supply voltage to Pin 14 activating the A/C clutch. During A/C operation, if the PCM determines that A/C clutch operation is not desireable, the WAC output will be grounded and the VCRM will turn off the A/C clutch. Under normal conditions, with the A/C off, the PCM will ground the WAC output.

Vehicle Power

When the ignition switch is turned to the start or run position, the VCRM supplies Vehicle Power (VPWR) to the EEC system and the PCM

Fig 1: Pinpoint Test XB Schematic

Courtesy of FORD MOTOR CO.

VCRM PIN USAGE AND WIRE COLORS

Pin	Pin Usage	Wire Color
1	Power Ground	BK
2	Power-to-Cooling Fan	LB
3	Power-to-Cooling Fan	LB
4	B(+)	Y
5	B(+)	Y
6	B(+)	Y
7	VPWR	R
8	Ground	BK/W
9	A/C Cyclic Switch	BK/Y
10	High Fuel Pump	BR/W
11	WOT A/C Cut-Off	PK/Y
12	ACP SIG RTN	LB/R

VCRM PIN USAGE AND WIRE COLORS

Pin	Pin Usage	Wire Color
13	A/C Clutch Return	GY/W
14	Power-to-A/C Clutch	P
15	A/C Clutch Ground	BK
16	Ground	BK/Y
17	IGN Start/Run	R/LG
18	Fuel Pump Circuit	LB/O
19	ACP Signal	DG/W
20	ACP VREF	O/LB
21	DATA(+)	T/O
22	Ground	BK/W
23	DATA(-)	PK/LB
24	Power-to-Fuel Pump	PK/BK

Fig 2: A/C Head Pressure Sensor Output Voltage Chart

Courtesy of FORD MOTOR CO.

XB1 CHECK BATTERY VOLTAGE

Key on, engine off
Measure voltage across battery terminals

Is voltage greater than 10.5 volts?

Yes	No
GO to XB2	SERVICE discharged battery. REFER to Charging/Electrical Group in Service Information

XB2 PCM GROUND FAULT ISOLATION

Key off
Breakout box installed, PCM connected
Measure voltage between B(+) post of the battery and SIG RTN (GY/R wire) in the Data Link Connector (DLC)

Is voltage greater than 10.5 volts and within 1.0 volt of the reading in XB1 ?

Yes	No
GO to XB10 (PCM ground circuits OK).	GO to XB3 (to check PCM ground circuits).

XB3 CHECK SIG RTN CONTINUITY

Key off
Breakout box installed
Disconnect PCM
Measure resistance between Test Pin 46 and SIG RTN in DLC

Is resistance less than 5.0 ohms?

Yes	No
GO to XB4	SERVICE open in SIG RTN circuit. REMOVE breakout box, RECONNECT PCM. RERUN Quick Test

XB4 CHECK PCM POWER GROUND CIRCUITS

Key off
Breakout box installed, PCM disconnected
Measure resistance between the negative battery post, and Test Pins 40 and 60 at the breakout box

Is resistance less than 5.0 ohms?

Yes	No
GO to XB5	SERVICE open PWR GND circuit. REMOVE breakout box, RECONNECT PCM. RERUN Quick Test

XB5 CHECK INTERNAL PCM GROUND CIRCUITS

Key off
Breakout box installed
Reconnect PCM
Measure resistance between Test Pin 46 and Test Pins 40 and 60 at the breakout box

Is resistance less than 5.0 ohms?

Yes	No
System Tests OK. VERIFY correct test results. REMOVE breakout box. RECONNECT PCM. RERUN Quick Test	REPLACE PCM. REMOVE breakout box. RERUN Quick Test

XB10 CHECK VPWR CIRCUIT CONTINUITY BETWEEN PCM AND VCRM

Key off
Breakout box installed, PCM disconnected
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Measure resistance between Pin 7 of the VCRM vehicle harness connector and Test Pins 37 and 57 at the breakout box

Is resistance less than 5.0 ohms?

Yes	No
GO to XB11	SERVICE open in VPWR circuit between PCM and VCRM. REMOVE breakout box. RECONNECT all components. RERUN Quick Test

XB11 CHECK FOR B(+) AND IGN START/RUN VOLTAGE TO VCRM

Key off
Breakout box installed, PCM disconnected
VCRM disconnected
Measure voltage between Pin 6 of the VCRM vehicle harness connector and the battery negative post
Key on
Measure voltage between Pin 17 of the VCRM vehicle harness connector and the battery negative post

Are both voltages greater than 10.5 volts?

Yes	No
Key off. GO to XB12	Key off. SERVICE open in B(+) or IGN START/RUN circuit. REMOVE breakout box. RECONNECT all components. RERUN Quick Test

XB12 CHECK VCRM GROUND (PIN 16)

Key off
Breakout box installed, PCM disconnected
VCRM disconnected
Measure resistance between Pin 16 of the VCRM vehicle harness connector and the battery negative post

Is resistance less than 5.0 ohms?

Yes	No
REPLACE VCRM. REMOVE breakout box. RECONNECT all components. RERUN Quick Test	SERVICE open GND circuit. REMOVE breakout box. RECONNECT all components. RERUN Quick Test

XB15 CONTINUOUS MEMORY DIAGNOSTIC TROUBLE CODE (DTC) 584: CLEAR AND ATTEMPT TO REGENERATE DTC

Continuous Memory DTC 584 indicates the VCRM PWR GND (Pin 1) is open. This could be due to a hard fault or an intermittent condition.

Possible causes:

Open VCRM PWR GND circuit.
Damaged VCRM

Clear Continuous Memory
Start engine
Turn A/C on, wait 15 seconds
A/C off
Engine off
Rerun Key On Engine Off (KOEO) Self-Test

Is Continuous Memory DTC 584 present?

Yes	No
DTC 584 is a hard fault. GO to XB16	DTC 584 is intermittent. GO to XB18

XB16 CHECK VCRM PWR GND CIRCUIT CONTINUITY

Key off
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Measure resistance between Pin 1 of the VCRM vehicle harness connector and the battery negative post

Is resistance less than 5.0 ohms?

Yes	No
REPLACE VCRM. RECONNECT all components. CLEAR Continuous Memory. START engine. A/C on, WAIT 15 seconds. Key off, A/C off. RERUN Quick Test	SERVICE open in VCRM PWR GND circuit. RECONNECT all components. CLEAR Continuous Memory. START engine. A/C on, WAIT 15 seconds. Key off, A/C off. RERUN Quick Test

XB18 CHECK VCRM PWR GND CIRCUIT

Key off
Visually check the VCRM PWR GND circuit (VCRM Pin 1) from the VCRM to the circuit's ground point. The VCRM PWR GND circuit is grounded to the RH side radiator support to a weld nut
Start engine
A/C on (to turn cooling fan on).
CAUTION: While performing this test, do not touch any moving/hot engine parts.
Shake, wiggle, bend the VCRM PWR GND circuit, between the VCRM and the circuit's ground point. An open circuit will be indicated by the fan speed increasing to 100% (although the open must be present for at least 5 seconds).
Lightly tap on VCRM to simulate road shock

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. CLEAR Continuous memory (DTC 584 should have been set). START engine. A/C on, WAIT 15 seconds. Key off, A/C off. RERUN Quick Test	Key off, A/C off. GO to XB19

XB19 CHECK VCRM PWR GND CIRCUIT

Key off
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Connect a test lamp between Pin 5 and Pin 1 of the VCRM vehicle harness connector
Observe test lamp for an indication of a fault while performing the following (the lamp will go out when a fault is found, indicating an open):
- Shake, wiggle, bend the VCRM PWR GND circuit between the VCRM vehicle harness connector and the circuit's ground point

Is fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. RECONNECT all components. START engine. A/C on, WAIT 15 seconds. A/C off, key off. RERUN Quick Test	Unable to isolate fault at this time. RECONNECT all components. For further diagnosis using the EEC-IV Monitor Box or Scan Tool, GO to appropriate article. For further diagnosis of this, or any other symptom, RETURN to appropriate article

XB20 CONTINUOUS MEMORY DIAGNOSTIC TROUBLE CODE (DTC) 581: CLEAR AND ATTEMPT TO REGENERATE DTC

Continuous Memory DTC 581 indicates that when the cooling fan was activated, the Power-to-Cooling Fan circuit exceeded the normal current draw. This could be due to a hard fault or an intermittent condition.

Possible causes:

Power-to-Cooling Fan circuit short to ground.
Damaged cooling fan motor.
Damaged VCRM.

Clear Continuous Memory
Start engine
Turn A/C on, wait 15 seconds
A/C off.
Engine off
Rerun KOEO Self-Test

Is Continuous Memory DTC 581 present?

Yes	No
DTC 581 is a hard fault. GO to XB21	DTC 581 is intermittent. GO to XB24

XB21 CHECK COOLING FAN MOTOR

Clear Continuous Memory again
Disconnect cooling fan motor
Start engine
Turn A/C on, wait 15 seconds (but no more than 20 seconds).
A/C off
Engine off
Rerun KOEO Self-Test

Is Continuous Memory DTC 581 present (disregard any other codes)?

Yes	No
GO to XB22	REPLACE cooling fan motor. RECONNECT all components. RERUN Quick Test

XB22 CHECK POWER-TO-COOLING FAN CIRCUIT FOR SHORT TO GROUND

Key off
Cooling fan motor disconnected
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Measure resistance between the power-to-cooling fan circuit at the cooling fan vehicle harness connector and the battery negative post
Is resistance greater than 10, 00 ohms?

Yes	No
REPLACE VCRM. RECONNECT all components. CLEAR Continuous Memory. START engine. TURN A/C on, wait 15 seconds. A/C off, key off. RERUN Quick Test	SERVICE power-to-cooling fan circuit short to ground. RECONNECT all components. CLEAR Continuous Memory. START engine. TURN A/C on, WAIT 15 seconds. A/C off, key off. RERUN Quick Test

XB24 CHECK POWER-TO-COOLING FAN CIRCUIT FOR INTERMITTENT SHORT TO GROUND

Key off
Visually check the power-to-cooling fan circuit from the VCRM to the cooling fan
Start engine
A/C on (to turn cooling fan on).
CAUTION: While performing this test, do not touch any moving/hot engine parts
Shake, wiggle, bend the power-to-cooling fan circuit from the VCRM to the cooling fan (as close as practical). A short to ground will be indicated by the fan turning off (the VCRM FMEM will turn the fan off when an over current condition exists).
Key off. A/C off

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. CLEAR Continuous Memory (DTC 581 should have been set). START engine. A/C on, WAIT 5 seconds. A/C off, key off. RERUN Quick Test	GO to XB25

XB25 CHECK VCRM CONNECTOR AND POWER-TO-COOLING FAN CIRCUIT

Key off
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Connect a test lamp between Pin 2 and Pin 4 of the VCRM vehicle harness connector
Observe test lamp for an indication of a fault while performing the following: (The lamp will be on, but not to full brightness. A short to ground will be indicated by the lamp getting brighter.)
- Shake, wiggle, bend the power-to-cooling fan circuit near the cooling fan.
Disconnect cooling fan. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.
Test lamp still connected between Pin 2 and Pin 4 of the VCRM vehicle harness connector
Observe test lamp for an indication of a fault while performing the following (the lamp will turn on, indicating a short to ground):
- Again, shake, wiggle, bend the power-to-cooling fan circuit from the VCRM vehicle harness connector to the cooling fan vehicle harness connector.

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. RECONNECT all components. START engine. A/C on, WAIT 5 seconds. A/C off, key off. RERUN Quick Test.	Unable to isolate fault at this time. RECONNECT all components. For further diagnosis using the EEC-IV Monitor Box or Scan Tool, GO to appropriate article. For further diagnosis of this, or any other symptom, RETURN to appropriate article

XB30 KEY ON ENGINE OFF DIAGNOSTIC TROUBLE CODE (DTC) 582: VERIFY COOLING FAN IS NOT ALWAYS ON

Key On Engine Off (KOEO) DTC 582 indicates an open or short to power in the power-to-cooling fan circuit.

Possible causes:

Open or short to power in the power-to-cooling fan circuit (harness).
Open cooling fan motor ground circuit
Open circuit in cooling fan
Damaged VCRM
NOTE: If KOEO DTC 587 is also present, refer to the EEC-IV DTC charts to address the 587 first. Also verify that the cooling fan was not turning during KOEO Self-Test. If the fan was turning, back voltage could be sent to the VCRM through the power-to-cooling fan circuit resulting in an invalid 582 DTC

Engine cooled down (so cooling fan would normally be off).
A/C and defroster off
Key on, engine off

Is cooling fan on?

Yes	No
Key off. GO to XB35 (to check for short to power).	Key off. GO to XB31 (to check for opens).

XB31 CHECK FOR VOLTAGE TO COOLING FAN

Key off
Disconnect cooling fan
Start engine
Turn A/C on
Measure voltage between the power-to-cooling fan circuit and ground circuit at the cooling fan vehicle harness connector

Is voltage greater than 6.0 volts?

Yes	No
Key off. REPLACE cooling fan. RERUN Quick Test	Key off. GO to XB32

XB32 CHECK COOLING FAN GROUND CIRCUIT CONTINUITY

Key off
Cooling fan disconnected
Measure resistance between the ground circuit at the cooling fan vehicle harness connector and the battery negative post

Is resistance less than 5.0 ohms?

Yes	No
GO to XB33	SERVICE open in cooling fan ground circuit. RECONNECT cooling fan. RERUN Quick Test

XB33 CHECK POWER-TO-COOLING FAN CIRCUIT CONTINUITY

Key off
Cooling fan disconnected
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Measure resistance between the power-to-cooling fan circuit at the cooling fan vehicle harness connector and Pins 2 and 3 of the VCRM vehicle harness connector

Is resistance less than 5.0 ohms?

Yes	No
REPLACE VCRM. RECONNECT all components. RERUN Quick Test	SERVICE open in power-to-cooling fan circuit. RECONNECT all components. RERUN Quick Test

XB35 CHECK POWER-TO-COOLING FAN CIRCUIT FOR SHORT TO POWER

Key off
Disconnect cooling fan
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Key on, engine off
Measure voltage between the power-to-cooling fan circuit at the cooling fan vehicle harness connector and the battery negative post

Is voltage less than 1.0 volt?

Yes	No
REPLACE VCRM. RECONNECT all components. RERUN Quick Test	SERVICE short to power in the power-to-cooling fan circuit. RECONNECT all components. RERUN Quick Test

XB40 CONTINUOUS MEMORY DIAGNOSTIC TROUBLE CODE (DTC) 578: CLEAR AND ATTEMPT TO REGENERATE DTC

Continuous Memory DTC 578 indicates the A/C Pressure (ACP) sensor VREF circuit is short to ground. This could be due to a hard fault or an intermittent condition

Possible causes:

ACP sensor VREF circuit short to ground
Damaged ACP sensor
Damaged VCRM

Clear Continuous Memory
Start engine, wait 15 seconds
Engine off
Rerun Key On Engine Off (KOEO) Self-Test

Is Continuous Memory DTC 578 present?

Yes	No
DTC 578 is a hard fault. GO to XB41	DTC 578 is intermittent. GO to XB44

XB41 CHECK ACP SENSOR

Clear Continuous Memory again
Key off
Disconnect ACP sensor
Start engine, wait 15 seconds
Engine off
Rerun KOEO Self-Test

Is Continuous Memory DTC 578 present (disregard any other codes)?

Yes	No
GO to XB42	REPLACE ACP sensor. RECONNECT all components. CLEAR Continuous Memory. START engine, WAIT 15 seconds. Key off. RERUN Quick Test

XB42 CHECK ACP VREF CIRCUIT FOR SHORT TO GND

Key off
ACP sensor disconnected
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Measure resistance between the ACP VREF circuit at the ACP sensor vehicle harness connector and the battery ground post

Is resistance greater than 10, 00 ohms?

Yes	No
REPLACE VCRM. RECONNECT all components. CLEAR Continuous Memory. START engine, WAIT 15 seconds. Key off. RERUN Quick Test	SERVICE ACP VREF circuit short to ground. RECONNECT all components. CLEAR Continuous Memory. START engine, WAIT 15 seconds. Key off. RERUN Quick Test

XB44 CHECK ACP VREF FOR INTERMITTENT SHORT TO GROUND

Key off
Visually check the ACP VREF circuit from the ACP sensor to the VCRM
Disconnect the ACP sensor. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Connect test lamp between Pin 6 and Pin 20 of the VCRM vehicle harness connector
Observe test lamp for an indication of a fault while performing the following (the lamp will come on when a fault is found, indicating a short to ground):
- Shake, wiggle, bend the ACP VREF circuit from the ACP sensor vehicle harness connector and the VCRM vehicle harness connector

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. RECONNECT all components. START engine, WAIT 15 seconds. Key off. RERUN Quick Test	Unable to isolate fault at this time. RECONNECT all components. For further diagnosis using the EEC-IV Monitor Box or Scan Tool, GO to appropriate article. For further diagnosis of this, or any other symptom, RETURN to appropriate article

XB50 CONTINUOUS MEMORY DIAGNOSTIC TROUBLE CODE (DTC) 579: CHECK ACP VREF AND ACP SIG RTN CIRCUITS

Continuous Memory DTC 579 indicates the A/C Pressure (ACP) sensor did not detect a sufficient change in A/C system pressure when the A/C was turned on or the ACP circuit is above maximum voltage. This could be due to a problem in the ACP sensor circuits or the A/C system, and could be a hard fault or an intermittent concern

Possible causes:

Open or shorted ACP sensor circuit
A/C system mechanical concern
Damaged ACP sensor
Damaged VCRM
Power-to-A/C clutch circuit open (DTC 586 also present)

NOTE: If Continuous Memory DTC 586 is also present, refer to the EEC-IV DTC charts to address the 586

Key off
Disconnect ACP sensor
Key on
Measure voltage between the ACP VREF and the ACP SIG RTN circuits at the ACP sensor vehicle harness connector
Key off

What was the voltage?

Fig 3: A/C Pressure Sensor Vehicle Harness Connector

Courtesy of FORD MOTOR CO.

Greater Than 6.0 volts	Less Than 4.0 volts	Between 4.0 And 6.0 volts
GO to XB62 (to check ACP VREF for short to power).	GO to XB63 (to check ACP VREF and ACP SIG RTN circuits).	GO to XB51 (ACP VREF and ACP SIG RTN circuits OK to sensor).

XB51 CHECK IF A/C CLUTCH WILL ENGAGE (ACP SENSOR CONNECTED)

Key off
Reconnect ACP sensor
Start engine
Turn A/C on, wait 30 seconds

Does the A/C clutch "click" on?

Yes	No
Key off, A/C off. GO to XB52 (ACP circuit is not open or short to power).	Key off, A/C off. GO to XB57 (to check if ACP circuit is OK).

XB52 CLEAR AND ATTEMPT TO REGENERATE DTC

Clear Continuous Memory
Attempt to reset DTC 579 by performing the following:
1. Start engine
2. A/C on, wait 20 seconds after A/C clutch engagement is heard ("click").
3. A/C off, wait 5 seconds
4. Repeat steps 2 and 3 four more times (a total of five A/C clutch engagements, with each engagement lasting about 20 seconds, must be seen by the VCRM during the same power-up to set DTC 579 for insufficient A/C pressure change).
A/C off
Engine off
Rerun Key On Engine Off (KOEO) Self-Test

Is Continuous Memory DTC 579 present?

Yes	No
DTC 579 is a hard fault. GO to XB53	The ACP sensor is now able to detect an A/C system pressure change. Either an intermittent ACP sensor circuit fault exists, or an A/C system intermittent or marginal mechanical condition exists. GO to XB66

XB53 CHECK A/C SYSTEM PRESSURE AND PRESSURE CHANGE

Key off
Install A/C System Manifold Gauge Set. Refer to the Climate Control Group of the Service Information for installation instructions
A/C off
Start engine
Note the A/C high pressure gauge reading
While monitoring the A/C high pressure gauge reading, turn the A/C on. Ten seconds after clutch engagement, note the pressure (the pressure should increase).
Key off
A/C off

Did the A/C high pressure gauge reading change more than 20 psi within 10 seconds of clutch engagement?

Yes	No
GO to XB54 (the A/C pressure changed as expected. ACP sensor and circuit will now be checked).	A/C system pressure did not change as expected. GO to the Climate Control Group of the Service Manual to check for A/C system mechanical concerns. After any service, CLEAR Continuous Memory. ATTEMPT to reset DTC 579 (refer to XB52 for procedure only). RERUN Quick Test

XB54 CHECK ACP SENSOR OUTPUT

Key off
Disconnect ACP sensor
A/C system Manifold Gauge Set installed
Jumper the ACP SIG RTN circuit between the ACP sensor vehicle harness connector and the ACP sensor connector
Jumper the ACP VREF circuit between the ACP sensor vehicle harness connector and the ACP sensor connector
Jumper the ACP signal circuit at the ACP sensor vehicle harness connector to the battery negative post
Connect a DVOM between the ACP signal circuit at the ACP sensor connector and the ACP SIG RTN circuit jumper wire
A/C off
Start engine
Note the A/C high pressure gauge reading and the ACP sensor voltage
While monitoring the ACP sensor voltage, turn the A/C on. Ten seconds after clutch engagement, note the voltage
A/C off
Key off

Did the ACP sensor voltage change more than 0.2 volts within 10 seconds of turning the A/C on?

NOTE: By listening to the A/C clutch, verify that it does not disengage during the 10 seconds of testing. If it does disengage, retest

Fig 4: Checking ACP Sensor Output

Courtesy of FORD MOTOR CO.

Yes	No
REMOVE jumper wires. GO to XB55.(ACP sensor is operational.)	REPLACE ACP sensor. REMOVE A/C system Manifold Gauge Set. REMOVE jumper wires. RECONNECT all components. CLEAR Continuous Memory. ATTEMPT to reset DTC 579 (REFER to XB52 for procedure only). RERUN Quick Test

XB55 CHECK ACP CIRCUIT FOR SHORT TO GROUND

Key off
ACP sensor disconnected
Disconnect VCRM
Measure resistance between the ACP circuit at the ACP sensor vehicle harness connector and the battery negative post
Measure resistance between the ACP circuit and the ACP SIG RTN circuit at the ACP sensor vehicle harness connector

Are both resistances greater than 10, 00 ohms?

Yes	No
REPLACE VCRM. REMOVE A/C system Manifold Gauge set. RECONNECT all components. CLEAR Continuous Memory. ATTEMPT to reset DTC 579 (refer to XB52 for procedure only). RERUN Quick Test	SERVICE ACP circuit short to ground or SIG RTN. REMOVE A/C system Manifold Gauge Set. RECONNECT all components. CLEAR Continuous Memory. ATTEMPT to reset DTC 579 (refer to XB52 for procedure only). RERUN Quick Test

XB57 CHECK FOR VOLTAGE TO A/C CLUTCH (USING TEST LAMP)

Key off
Disconnect A/C Cyclic Pressure Switch. Install a jumper wire in the A/C Cyclic Pressure Switch vehicle harness connector (to complete the circuit).
Disconnect A/C clutch
Connect a non-powered test lamp between the Power-to-A/C Clutch circuit and the A/C clutch ground circuit at the A/C clutch vehicle harness connector.
Start engine
A/C on, wait 10 seconds

Is test lamp on?

Yes	No
REMOVE test lamp and jumper. RECONNECT all components. GO to the Climate Control Group of the Service Manual to check for A/C system mechanical concerns (ex. A/C clutch air gap, etc.). After any service, CLEAR Continuous Memory. Attempt to reset DTC 579 (REFER to XB52 for procedure only). RERUN Quick Test	GO to XB58 (to check ACP circuits).

XB58 CHECK CONTINUITY OF ACP CIRCUIT

Key off
Disconnect ACP sensor
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Measure resistance between the ACP circuit at the ACP sensor vehicle harness connector and Pin 19 at the VCRM vehicle harness connector

Is resistance less than 5.0 ohms?

Yes	No
GO to XB59	SERVICE open ACP circuit. REMOVE test lamp and jumper. RECONNECT all components. CLEAR Continuous Memory. A/C off, START engine. TURN A/C on, WAIT 20 seconds. Key off, A/C off. RERUN Quick Test

XB59 CHECK ACP CIRCUIT FOR SHORT TO POWER

Key off
ACP sensor disconnected
VCRM disconnected
Key on
Measure voltage between the ACP circuit at the ACP sensor vehicle harness connector and the battery negative post
Key off

Was the voltage less than 1.0 volt?

Yes	No
GO to XB60	SERVICE ACP circuit short to power. REMOVE test lamp and jumper. RECONNECT all components. CLEAR Continuous Memory. A/C off, START engine. TURN A/C on, WAIT 20 seconds. Key off, A/C off. RERUN Quick Test

XB60 CHECK IF TEST LAMP AT A/C CLUTCH WILL TURN ON WITH ACP CIRCUIT GROUNDED

Key off
ACP sensor disconnected
Reconnect VCRM
A/C Cyclic Pressure Switch disconnected. Jumper wire installed in vehicle harness connector
A/C clutch disconnected
Non-powered test lamp connected between the Power-To-A/C clutch circuit and A/C clutch ground circuit at the A/C clutch vehicle harness connector
Connect a jumper wire between the ACP signal circuit at the ACP sensor vehicle harness connector and the battery negative post
Start engine
A/C on, wait 10 seconds

Is test lamp on?

Fig 5: ACP Sensor Vehicle Harness Connector

Courtesy of FORD MOTOR CO.

Yes	No
Key off. REPLACE ACP sensor. REMOVE test lamp and jumpers. RECONNECT all components. CLEAR continuous memory. A/C off. START engine. TURN A/C on, WAIT 20 seconds. Key off, A/C off. RERUN Quick Test	Key off. REPLACE VCRM. REMOVE test lamp and jumpers. RECONNECT all components. CLEAR continuous memory. A/C off. START engine. TURN A/C on. WAIT 20 seconds. Key off, A/C off. RERUN Quick Test.

XB62 CHECK ACP VREF FOR SHORT TO POWER

Key off
ACP sensor disconnected
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Key on
Measure voltage between the ACP VREF circuit at the ACP sensor vehicle harness connector and the battery negative post
Key off

Was the voltage less than 1.0 volt?

Yes	No
REPLACE VCRM. RECONNECT all components. CLEAR Continuous Memory. ATTEMPT to reset DTC 579 (REFER to XB52 for procedure only). RERUN Quick Test	SERVICE ACP VREF circuit short to power. RECONNECT all components. CLEAR Continuous Memory. ATTEMPT to reset DTC 579 (REFER to XB52 for procedure only). RERUN Quick Test

XB63 CHECK ACP SIG RTN AND ACP VREF CIRCUIT CONTINUITY

Key off
ACP sensor disconnected
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Measure resistance between the ACP SIG RTN circuit at the ACP sensor vehicle harness connector and Pin 12 of the VCRM vehicle harness connector
Measure resistance between the ACP VREF circuit at the ACP sensor vehicle harness connector and Pin 20 of the VCRM vehicle harness connector

Are both resistances less than 5.0 ohms?

Yes	No
GO to XB64	SERVICE open in ACP VREF or ACP SIG RTN circuit. RECONNECT all components. CLEAR Continuous Memory. ATTEMPT to reset DTC 579 (REFER to XB52 for procedure only). RERUN Quick Test

XB64 CHECK ACP SIG RTN FOR SHORT TO VREF

Key off
ACP sensor disconnected
VCRM disconnected
Measure resistance between the ACP SIG RTN circuit and the ACP VREF circuit at the ACP sensor vehicle harness connector

Is resistance greater than 10, 00 ohms?

Yes	No
GO to XB65	SERVICE ACP SIG RTN short to ACP VREF. RECONNECT all components. CLEAR Continuous Memory. ATTEMPT to reset DTC 579 (REFER to XB52 for procedure only). RERUN Quick Test

XB65 CHECK ACP SIG RTN FOR SHORT TO POWER

Key off
ACP sensor disconnected
VCRM disconnected
Key on
Measure voltage between the ACP SIG RTN circuit at the ACP sensor vehicle harness connector and the battery negative post
Key off

Was voltage less than 1.0 volt?

Yes	No
REPLACE VCRM. RECONNECT all components. CLEAR Continuous Memory. ATTEMPT to reset DTC 579 (REFER to XB52 for procedure only). RERUN Quick Test	SERVICE ACP SIG RTN circuit short to power. RECONNECT all components. CLEAR Continuous Memory. ATTEMPT to reset DTC 579 (REFER to XB52 for procedure only). RERUN Quick Test

XB66 DOES THE A/C APPEAR TO COOL PROPERLY

Does the A/C appear to cool properly?

Yes	No
GO to XB67 (to check for intermittent ACP circuits)	GO to the Climate Control Group of the Service Information to check the mechanical operation of the A/C system (low refrigerant charge, intermittent concerns, etc). If all checks are OK, RETURN to XB67 to check for intermittent ACP circuits

XB67 CHECK ACP VREF AND ACP SIG RTN CIRCUITS FOR INTERMITTENT OPENS

Key off
A/C off
Disconnect ACP sensor. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Key on
Connect test lamp between ACP VREF and ACP SIG RTN circuits at the ACP sensor vehicle harness connector (if test lamp will not light sufficiently, use DVOM to monitor 5 volts)
Observe test lamp/DVOM for an indication of a fault while performing the following (the test lamp will go out, or the DVOM voltage will drop, indicating an open circuit):
- Shake, wiggle, bend the ACP VREF and ACP SIG RTN circuits between the ACP sensor vehicle harness connector and the VCRM
- Lightly tap the VCRM (to simulate road shock)
Key off

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. RECONNECT all components. START engine, A/C on. WAIT 20 seconds. Key off. RERUN Quick Test	GO to XB68

XB68 CHECK ACP SIGNAL FOR INTERMITTENT SHORT TO GROUND OR POWER

Key off
ACP sensor disconnected
Connect test lamp or DVOM (which ever was used in previous step) between ACP VREF and ACP signal circuit at the ACP sensor vehicle harness connector
Key on
Observe test lamp/DVOM for an indication of a fault while performing the following (the lamp will come on, or DVOM will read 5V, indicating an ACP signal short to ground):
- Shake, wiggle, bend the ACP signal from the ACP sensor vehicle harness connector to the VCRM
- Lightly tap the VCRM (to simulate road shock).
Reconnect test lamp/DVOM between ACP SIG RTN and ACP signal circuit at the ACP sensor vehicle harness connector
Again, observe test lamp/DVOM for an indication of a fault while performing the following (the test lamp will come on, or DVOM voltage will increase, indicating an ACP signal short to power)
- Shake, wiggle, bend the ACP signal from the ACP sensor vehicle harness connector to the VCRM
- Lightly tap the VCRM (to simulate road shock).
Key off

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. RECONNECT all components. START engine. A/C on, WAIT 20 seconds. A/C off, key off. RERUN Quick Test	GO to XB69

XB69 CHECK ACP SIGNAL FOR INTERMITTENT OPEN

Key off
ACP sensor disconnected
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Connect DVOM (to measure resistance) between Pin 19 at the VCRM vehicle harness connector and the ACP signal circuit at the ACP sensor vehicle harness connector. Resistance reading should be less than 5.0 ohms
Observe DVOM for an indication of a fault while performing the following (the DVOM will read greater than 5.0 ohms when a fault is detected, indicating an open circuit):
- Shake, wiggle, bend the ACP signal circuit from the VCRM vehicle harness connector to the ACP sensor vehicle harness connector

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. RECONNECT all components. START engine. A/C on, WAIT 20 seconds. Key off. RERUN Quick Test	Unable to isolate fault at this time. RECONNECT all components. For further diagnosis using the EEC-IV Monitor Box or Scan Tool, GO to appropriate article. For further diagnosis of this, or any other symptom, RETURN to appropriate article

XB70 CONTINUOUS MEMORY DIAGNOSTIC TROUBLE CODE (DTC) 585: CLEAR AND ATTEMPT TO REGENERATE DTC

Continuous Memory DTC 585 indicates that when the A/C was turned on, the power-to-A/C clutch circuit exceeded the normal current draw. This could be due to a hard fault or an intermittent condition

Possible causes:

Power-to-A/C clutch circuit short to ground
Damaged A/C clutch
Damaged VCRM

Clear Continuous Memory
Start engine
Turn A/C on, wait 15 seconds
A/C off
Engine off
Rerun Key On Engine Off (KOEO) Self-Test

Is Continuous Memory DTC 585 present?

Yes	No
DTC 585 is a hard fault. GO to XB71	DTC 585 is intermittent. GO to XB74

XB71 CHECK A/C CLUTCH

Clear Continuous Memory again
Disconnect A/C clutch
Start engine
Turn A/C on, wait 15 seconds
A/C off
Engine off
Rerun KOEO Self-Test

Is Continuous Memory DTC 585 present (ignore DTC 586 if received)?

Yes	No
GO to XB72	CHECK any A/C clutch external wiring for shorts to ground. If OK, REPLACE A/C clutch (refer to Climate Control Group in Service Information). RECONNECT all components. CLEAR Continuous Memory (if necessary). RERUN Quick Test

XB72 CHECK POWER-TO-A/C CLUTCH CIRCUIT FOR SHORT TO GROUND

Key off
A/C clutch disconnected
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Measure resistance between the power-to-A/C clutch circuit at the A/C clutch vehicle harness connector and the battery negative post

Is resistance greater than 10, 00 ohms?

Yes	No
REPLACE VCRM. RECONNECT all components. CLEAR Continuous Memory. START engine. TURN A/C on, WAIT 15 seconds. A/C off. Key off. RERUN Quick Test	SERVICE power-to-A/C clutch circuit short to ground. RECONNECT all components. CLEAR Continuous Memory. START engine. TURN A/C on, WAIT 15 seconds. A/C off. Key off. RERUN Quick Test

XB74 CHECK POWER-TO-A/C CLUTCH CIRCUIT FOR INTERMITTENT SHORT TO GROUND

Key off
Visually check the power-to-A/C clutch circuit from the VCRM to the A/C clutch
Start engine
A/C on
CAUTION: While performing this test, do not touch any moving/hot engine parts
Shake, wiggle, bend the power-to-A/C clutch from the A/C clutch to the VCRM. A short to ground will be indicated by the A/C clutch disengaging for other than normal cyclic pressure switch operation (the VCRM FMEM will turn the A/C off when an over current condition exists).
Key off, A/C off

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. CLEAR Continuous Memory (DTC 585 should have been set). START engine. A/C on, WAIT 5 seconds. A/C off, key off. RERUN Quick Test	GO to XB75

XB75 CHECK POWER-TO-A/C CLUTCH CIRCUIT FOR INTERMITTENT SHORT TO GROUND

Key off
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Disconnect A/C clutch. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Connect a test lamp between Pin 4 and Pin 14 of the VCRM vehicle harness connector
Observe test lamp for an indication of a fault while performing the following (the lamp will turn on when a fault is detected, indicating a short to ground):
- Shake, wiggle, bend the power-to-A/C clutch circuit from the A/C clutch vehicle harness connector to the VCRM vehicle harness connector

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. RECONNECT all components. START engine. A/C on, WAIT 5 seconds. A/C off, key off. RERUN Quick Test	Unable to isolate fault at this time. RECONNECT all components. For further diagnosis using the EEC-IV Monitor Box or Scan Tool, GO to appropriate article. For further diagnosis of this, or any other symptom, RETURN to appropriate article.

XB80 CONTINUOUS MEMORY DIAGNOSTIC TROUBLE CODE (DTC) 586: CLEAR AND ATTEMPT TO REGENERATE DTC

Continuous Memory DTC 586 indicates an open or short to power in the power-to-A/C clutch circuit. This could be due to a hard fault or an intermittent condition

Possible causes:

Open or short to power in the power-to-A/C clutch circuit (harness)
Open A/C clutch ground circuit (to VCRM Pin 13)
Open VCRM A/C ground (VCRM Pin 15 to weld nut on LH side radiator support).
Open circuit in A/C clutch
Damaged VCRM

Clear Continuous Memory
A/C off, defroster off (testing for DTC 586 is done only with the A/C off).
Start engine, wait 15 seconds
Engine off
Rerun Key On Engine Off (KOEO) Self-Test

Is Continuous Memory DTC 586 present?

Yes	No
DTC 586 is a hard fault. GO to XB81	DTC 586 is intermittent. GO to XB85

XB81 CHECK POWER-TO-A/C CLUTCH CIRCUIT FOR SHORT TO POWER

Key off
Disconnect A/C clutch.
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Key on
Measure voltage between the power-to-A/C clutch circuit at the A/C clutch vehicle harness connector and the battery negative post
Key off

Was the voltage less than 1.0 volt?

Yes	No
GO to XB82	SERVICE power-to-A/C clutch circuit for short to power. RECONNECT all components. CLEAR Continuous Memory. A/C off, defroster off. START engine. WAIT 15 seconds. Key off. RERUN Quick Test

XB82 CHECK CONTINUITY OF POWER-TO-A/C CLUTCH, A/C CLUTCH GROUND AND VCRM A/C GROUND CIRCUITS

Key off
A/C clutch disconnected
VCRM disconnected
Measure resistance between Pin 14 of the VCRM vehicle harness connector and the power-to-A/C clutch circuit at the A/C clutch vehicle harness connector
Measure resistance between Pin 13 of the VCRM vehicle harness connector and the A/C clutch ground circuit at the A/C clutch vehicle harness connector
Measure resistance between Pin 15 of the VCRM vehicle harness connector and the battery negative post

Are all resistances less than 5.0 ohms?

Yes	No
GO to XB83	SERVICE open in applicable circuit. RECONNECT all components. CLEAR Continuous Memory. A/C off, defroster off. START engine, WAIT 15 seconds. Key off. RERUN Quick Test

XB83 CHECK CONTINUITY OF A/C CLUTCH

Key off
A/C clutch disconnected
VCRM disconnected
Measure resistance of the A/C clutch coil (between the power-to-A/C clutch and A/C clutch ground pins at the A/C clutch connector).

Is resistance less than 10 ohms?

Yes	No
REPLACE VCRM. RECONNECT all components. CLEAR Continuous Memory. A/C off, defroster off. START engine, WAIT 15 seconds. Key off. RERUN Quick Test	REPLACE A/C clutch (refer to Climate Control Group of the Service Manual). RECONNECT all components. CLEAR Continuous Memory. A/C off, defroster off. START engine, WAIT 15 seconds. Key off. RERUN Quick Test

XB85 CHECK POWER-TO-A/C CLUTCH, A/C CLUTCH GROUND AND VCRM A/C GROUND CIRCUITS FOR INTERMITTENT OPENS

Key off
Visually check the power-to-A/C clutch and A/C clutch ground (Pin 13) circuits from the VCRM to the A/C clutch. Also check the VCRM A/C ground circuit (Pin 15) from the VCRM to its ground point (weld nut on LH side radiator support)
Start engine
A/C on
CAUTION: While performing this test, do not touch any moving/hot engine parts
Shake, wiggle, bend the power-to-A/C clutch, A/C clutch ground and VCRM A/C ground circuits. An open will be indicated by the A/C clutch disengaging for other than normal cyclic pressure switch operation
Key off, A/C off

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. RERUN Quick Test	GO to XB86

XB86 CHECK POWER-TO-A/C CLUTCH CIRCUIT FOR INTERMITTENT SHORT TO POWER

A/C off
Key on
Shake, wiggle, bend the power-to-A/C clutch circuit between the VCRM and A/C clutch (especially in the vicinity of power circuits). A short to power will be indicated by the A/C clutch engaging
Key off

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. RERUN Quick Test	GO to XB87

XB87 CHECK POWER-TO-A/C CLUTCH, A/C CLUTCH GROUND AND VCRM A/C GROUND CIRCUITS AGAIN FOR INTERMITTENT OPENS

Key off
Disconnect A/C clutch. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Connect a test lamp between the power-to-A/C clutch and A/C clutch ground circuits at the A/C clutch vehicle harness connector
Start engine
A/C on
CAUTION: While performing this test, do not touch any moving/hot engine parts
Observe test lamp for an indication of a fault while performing the following (the lamp will go out when a fault is detected, indicating an open circuit):
- Shake, wiggle, bend the power-to-A/C clutch, A/C clutch ground and VCRM A/C ground circuits
- Lightly tap on the VCRM (to simulate road shock)
Key off, A/C off

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. RECONNECT all components. RERUN Quick Test	Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary. If OK, unable to isolate fault at this time. RECONNECT all components. For further diagnosis using the EEC-IV Monitor Box or Scan Tool, GO to appropriate article. For further diagnosis of this, or any other symptom, RETURN to appropriate article

XB90 NO A/C (WITH DTC 111): CHECK FOR VOLTAGE AT A/C CLUTCH

NOTE: Before proceeding with "No A/C" diagnostics, verify integrity of related fuse(s) in fuse panel

Key off
Disconnect A/C clutch
Connect a non-powered test lamp between the power-to-A/C clutch circuit and the A/C clutch ground circuit at the A/C clutch vehicle harness connector
Start engine
A/C on, wait 10 seconds

Is test lamp on (allow time for normal on/off cycling of the Cyclic Pressure Switch)?

Yes	No
EEC-IV system OK. REMOVE test lamp and RECONNECT A/C clutch. REFER to the Climate Control Group of the Service Information to check for A/C system mechanical problems, etc	GO to XB91

XB91 CHECK IF PCM IS RECEIVING AND RECOGNIZING ACCS (PIN 10) INPUT

Key off
Remove test lamp
Reconnect A/C clutch
A/C on
Perform Key On Engine Off Self-Test

Is Key On Engine Off DTC 539 present?

Yes	No
The PCM is receiving and recognizing the ACCS input. GO to XB92 (to verify the VCRM is receiving the A/C demand voltage).	The PCM is not receiving or recognizing the ACCS input. GO to XB96

XB92 CHECK FOR A/C DEMAND VOLTAGE AT VCRM

Key off
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
A/C on
Key on
Measure voltage between Pin 9 of the VCRM vehicle harness connector and the battery negative post
Key off

Was voltage greater than 10.5 volts?

Yes	No
GO to XB93 (to check for WAC circuit short to ground).	SERVICE open in A/C demand circuit between VCRM and splice to PCM. RECONNECT all components. RE-EVALUATE symptom

XB93 CHECK WAC CIRCUIT FOR SHORT TO GROUND

Key off
VCRM disconnected
Disconnect PCM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Measure resistance between Pin 11 of the VCRM vehicle harness connector and the battery negative post

Is resistance greater than 10, 00 ohms?

Yes	No
GO to XB94	SERVICE WAC circuit short to ground. RECONNECT all components. RE-EVALUATE symptom

XB94 VERIFY WAC CIRCUIT IS NOT SHORT TO GROUND IN PCM

Key off
PCM disconnected
Reconnect VCRM
Disconnect A/C clutch
Again, connect a non-powered test lamp between the power-to-A/C clutch circuit and the A/C clutch ground circuit at the A/C clutch vehicle harness connector
A/C on
Key on

Is test lamp on?

Yes	No
REPLACE PCM. RECONNECT all components. RE-EVALUATE symptom	REPLACE VCRM. RECONNECT all components. RE-EVALUATE symptom

XB96 CHECK FOR A/C DEMAND VOLTAGE FROM ELECTRONIC AUTOMATIC TEMPERATURE CONTROL (EATC) MODULE AT A/C CYCLIC PRESSURE SWITCH

Key off
Disconnect A/C cyclic pressure switch
A/C on
Key on
Measure voltage between the circuit from the EATC module at the A/C cyclic pressure switch vehicle harness connector and the battery negative post
Key off
A/C off

Was voltage greater than 10.5 volts?

Yes	No
GO to XB97	VERIFY power supply to, and operation of, the EATC module. REFER to the Climate Control Group of the Service Manual. If OK, SERVICE open between EATC module and A/C cyclic pressure switch. RECONNECT all components. RE-EVALUATE symptom

XB97 CHECK A/C CYCLIC PRESSURE SWITCH CONTINUITY

Key off
A/C cyclic pressure switch disconnected
Measure continuity of the A/C cyclic pressure switch

Is resistance less than 5.0 ohms?

Yes	No
GO to XB98	GO to the Climate Control Group of the Service Information to check A/C system pressure, A/C cyclic pressure switch operation, etc

XB98 CHECK CONTINUITY BETWEEN A/C CYCLIC PRESSURE SWITCH AND PCM (PIN 10)

Key off
A/C cyclic pressure switch disconnected
Disconnect PCM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Install breakout box, leave PCM disconnected
Measure continuity between test Pin 10 at the breakout box and the circuit to the PCM/VCRM at the A/C Cyclic Pressure Switch vehicle harness connector

Is resistance less than 5.0 ohms?

Yes	No
REPLACE PCM. REMOVE breakout box. RECONNECT all components. RE-EVALUATE symptom	SERVICE open circuit between the A/C cyclic pressure switch and the PCM. REMOVE breakout box. RECONNECT all components. RERUN Quick Test

XB100 LACK OF POWER (WITH A/C ON): VERIFY WAC IS ABLE TO TURN OFF A/C CLUTCH

Start engine
A/C on
Perform a brief wide open throttle (WOT) and return to idle
The A/C clutch should disengage during the WOT, then a few seconds after returning to idle, the A/C clutch should reengage (a "click" sound should be heard when the clutch reengages).
Repeat test if necessary to verify results

NOTE: If the clicking sound cannot be heard, it may be necessary to disconnect the A/C clutch. With a test lamp connected to the Power-to-A/C clutch circuit and the GND circuit at the A/C clutch vehicle harness connector, observe the test lamp while performing the brief WOT. The test lamp should go off during the WOT, then come back on a few seconds after returning to idle

Does the A/C clutch or test lamp work as indicated?

Yes	No
The WAC circuit is operating properly. RETURN to appropriate articlefor other possible causes	The WAC circuit is not turning the A/C clutch off. GO to XB101

XB101 CHECK WAC CIRCUIT HARNESS CONTINUITY

Key off
Disconnect PCM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Install breakout box, leave PCM disconnected
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Measure resistance between Test Pin 54 at the breakout box and Pin 11 of the VCRM vehicle harness connector

Is resistance less than 5.0 ohms?

Yes	No
GO to XB102	SERVICE open WAC circuit. REMOVE breakout box. RECONNECT all components. RE-EVALUATE symptom

XB102 CHECK WAC CIRCUIT FOR SHORT TO POWER

Key off
Breakout box installed, PCM disconnected
VCRM disconnected
Key on
Measure voltage between Test Pin 54 and Test Pin 40 at the breakout box
Key off

Was voltage less than 1.0 volt?

Yes	No
GO to XB103	SERVICE short to power in WAC circuit. REMOVE breakout box. RECONNECT all components. RE-EVALUATE symptom

XB103 CHECK VCRM WAC CIRCUITRY

Key off
Breakout box installed, PCM disconnected
Reconnect VCRM
Key on
A/C on
Connect a jumper wire to Test Pin 54. While listening to the A/C clutch, connect and disconnect the other end of the jumper to Test Pin 40 a couple times
Key off
A/C off

Does the A/C clutch disengage and engage as the jumper wire is connected and disconnected?

Yes	No
REPLACE PCM. REMOVE breakout box. RECONNECT all components. RE-EVALUATE symptom	REPLACE VCRM. REMOVE breakout box. RECONNECT all components. RE-EVALUATE symptom

XB110 KEY ON ENGINE OFF DIAGNOSTIC TROUBLE CODE (DTC) 556: DOES ENGINE START?

Key On Engine Off DTC 556 indicates a fuel pump primary circuit failure

Possible causes:

No Start:

Open or short to power in FP circuit
Damaged VCRM
Damaged PCM

Engine Starts:

Short to ground in FP circuit
Damaged VCRM
Damaged PCM

Does the engine start?

Yes	No
GO to XB115 (to check for short to ground)	GO to XB111 (to check for opens and short to power).

XB111 CHECK FUEL PUMP (FP) CIRCUIT CONTINUITY

Key off
Disconnect PCM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Install breakout box, leave PCM disconnected
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Measure continuity between Test Pin 22 at the breakout box and Pin 18 of the VCRM vehicle harness connector

Is resistance less than 5.0 ohms?

Yes	No
GO to XB112	SERVICE open in FP circuit. REMOVE breakout box. RECONNECT all components. RERUN Quick Test

XB112 CHECK FP CIRCUIT FOR SHORT TO POWER

Key off
Breakout box installed, PCM disconnected
VCRM disconnected
Key on
Measure voltage between Test Pin 22 and Test Pin 40
Key off

Was voltage less than 1.0 volt?

Yes	No
GO to XB113	SERVICE FP circuit short to power. REMOVE breakout box. RECONNECT all components. RERUN Quick Test

XB113 CHECK VCRM FP CIRCUIT

Key off
Breakout box installed, PCM disconnected
Reconnect VCRM
Jumper Test Pin 22 to Test Pin 40 at the breakout box
Key on

Does the fuel pump run?

Yes	No
Key off. REMOVE jumper. REPLACE PCM. REMOVE breakout box. RECONNECT all components. RERUN Quick Test	Key off. REMOVE jumper. REPLACE VCRM. REMOVE breakout box. RECONNECT all components. RERUN Quick Test

XB115 CHECK PCM FOR SHORT TO GND

Key off
Disconnect PCM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Key on

Does the fuel pump run?

Yes	No
Key off. GO to XB116	Key off. REPLACE PCM. RECONNECT all components. RERUN Quick Test

XB116 CHECK FUEL PUMP (FP) CIRCUIT FOR SHORT TO GROUND

Key off
Install breakout box, leave PCM disconnected
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Measure resistance between Test Pin 22 and Test Pin 40 at the breakout box

Is resistance greater than 10, 00 ohms?

Yes	No
REPLACE VCRM. REMOVE breakout box. RECONNECT all components. RERUN Quick Test	SERVICE FP circuit short to ground. REMOVE breakout box. RECONNECT all components. RERUN Quick Test

XB120 KEY ON ENGINE OFF DIAGNOSTIC TROUBLE CODE (DTC) 542: WILL ENGINE START AND IDLE FOR ONE MINUTE?

Key On Engine Off DTC 542 indicates that one of the following has occurred:

No Start:

Inertia Fuel Shutoff (IFS) switch not reset or electrically open
Open in power-to-pump circuit between the FPM splice and the fuel pump
Poor fuel pump ground
Open circuit in fuel pump

Engine Starts:

Power-to-pump/FMP circuit short to power
High Speed Fuel Pump (HFP) relay contacts stuck closed
HFP circuit (VCRM Pin 10) short to ground
Open FPM circuit between PCM and power-to-pump splice
Left HO2S short to power
Damaged VCRM
Damaged PCM

Will the engine start and idle for one minute?

Yes	No
GO to XB121	GO to XB130 (to check for open in power-to-pump circuit between FPM splice and fuel pump ground. If engine starts but stalls, open is between FPM splice and HFP relay splice).

XB121 VERIFY THAT FUEL PUMP IS OFF

Key on, wait 5 seconds
Listen for motor noise from fuel pump

Is fuel pump off?

Yes	No
Key off. GO to XB126 (to check FPM circuit continuity and HO2S for short to power)	Key off. GO to XB122 (to check power-to-pump/FPM circuit short to power or HFP circuit short to ground).

XB122 CHECK VCRM

Key off
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Key on

Is fuel pump off?

Yes	No
Key off. REPLACE VCRM. RECONNECT all components. RERUN Quick Test	Key off. GO to XB123

XB123 CHECK HFP RELAY AND CIRCUITS

Key off
VCRM disconnected
Disconnect HFP relay
Key on

Is fuel pump off?

Yes	No
Key off. GO to XB124 (to check HFP circuit).	Key off. SERVICE short to power in power-to-pump/FPM circuit. RECONNECT all components. RERUN Quick Test

XB124 CHECK HFP CIRCUIT FOR SHORT TO GND

Key off
VCRM disconnected
HFP relay disconnected
Measure resistance between Pin 10 at the VCRM vehicle harness connector and the battery negative post

Is resistance greater than 10, 00 ohms?

Yes	No
REPLACE HFP relay. RECONNECT all components. RERUN Quick Test	SERVICE HFP circuit short to ground. RECONNECT all components. RERUN Quick Test

XB126 CHECK FPM CIRCUIT CONTINUITY

Key off
Disconnect PCM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Install breakout box, leave PCM disconnected
Disconnect High Speed Fuel Pump (HFP) relay
Measure resistance between Test Pin 8 at the breakout box and the power-to-pump circuit at the HFP relay vehicle harness connector

Is resistance less than 5.0 ohms?

Fig 6: HFP Relay Vehicle Harnessd Connector

Courtesy of FORD MOTOR CO.

Yes	No
GO to XB127	SERVICE open in FPM circuit between PCM and splice to power-to-pump circuit. REMOVE breakout box. RECONNECT all components. RERUN Quick Test

XB127 CHECK LEFT HO2S FOR SHORT TO POWER

NOTE: Due to the internal circuitry of the PCM, a left HO2S signal short to power could produce DTCs 524/542/543

Key off
Disconnect left HO2S
Measure resistance between HO2S signal pin and key power pin at the HO2S connector

Is resistance greater than 10, 00 ohms?

Fig 7: Checking Left HO2S For Short To Power

Courtesy of FORD MOTOR CO.

Yes	No
GO to XB128	REPLACE left HO2S. RECONNECT all components. RERUN Quick Test

XB128 CHECK LEFT HO2S CIRCUIT FOR SHORT TO POWER

Key off
Left HO2S disconnected
Disconnect PCM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Key on
Measure voltage between the HO2S signal at the HO2S vehicle harness connector and the battery negative post
Key off

Was voltage less than 2.0 volts?

Fig 8: Checking Left HO2S For Short To Power

Courtesy of FORD MOTOR CO.

Yes	No
REPLACE PCM. RECONNECT all components. RERUN Quick Test	SERVICE left HO2S circuit short to power. RECONNECT all components. RERUN Quick Test. CLEAR Keep Alive Memory

XB130 CHECK INERTIA FUEL SHUTOFF (IFS) SWITCH

Key off
Disconnect IFS switch (verify switch is reset).
Measure resistance between the C (common) and NC (normally closed) pins of the IFS switch

Is resistance less than 5.0 ohms?

Yes	No
RECONNECT IFS switch. REFER to the Fuel/Engine Group of the Service Manual to check for open in power-to-pump circuit from FPM splice to fuel pump, open circuit in fuel pump, poor fuel pump ground, etc. After service, RERUN Quick Test	RESET or REPLACE IFS switch. RECONNECT all components. RERUN Quick Test

XB135 KEY ON ENGINE OFF DIAGNOSTIC TROUBLE CODES (DTCS) 524/543. CONTINUOUS MEMORY DTC 583: IS CONTINUOUS MEMORY DTC 583 PRESENT?

Key On Engine Off DTCs 524/543 indicate that when the PCM commanded the fuel pump on, voltage was not detected on FPM (PCM Pin 8). Although DTC 524 refers to the low speed output (VCRM Pin 24) and DTC 543 refers to the high speed output, it is not possible to distinguish between circuits due to the vehicle wiring and fuel pump operating strategy

Continuous Memory DTC 583 indicates that when the fuel pump was activated, the power-to-pump circuit exceeded the normal current draw. This could be due to a hard fault or an intermittent condition

Possible causes are:

Without DTC 583:

Open in power-to-pump circuit between VCRM and FPM splice
Open in B(+) supply to VCRM (Pins 4 and 5).
Left HO2S short to power

With DTC 583:

Power-to-pump/FPM circuit short to ground

Is Continuous Memory DTC 583 present?

Yes	No
GO to XB136	GO to XB144

XB136 CLEAR AND ATTEMPT TO REGENERATE DTC 583

Key off
Clear Continuous Memory
Start or attempt to start engine (if engine will not start, crank for 5 seconds).
Rerun Key On Engine Off (KOEO) Self-Test

Is Continuous Memory DTC 583 present?

Yes	No
DTC 583 is a hard fault. GO to XB139 (to check power-to-pump/FPM for short to ground).	DTC 583 is intermittent. GO to XB137

XB137 WERE KOEO DTC 524 AND/OR 543 PRESENT IN XB136?

Were KOEO DTC 524 and/or 543 received from KOEO Self-Test in XB136?

Yes	No
GO to XB144. Be aware that an overcurrent condition (short to GND) was present sometime during the last 80 warm-up cycles	GO to XB147

XB139 ATTEMPT TO ISOLATE SHORT TO GROUND

Key off
Again, clear Continuous Memory
Unplug Inertia Fuel Shutoff (IFS) switch
Crank engine for 5 seconds
Rerun KOEO Self-Test

Is Continuous Memory DTC 583 present (disregard other codes)?

Yes	No
GO to XB140	GO to the Fuel/Engine Group of the Service Information to check for short to ground in power-to-pump circuit (IFS switch to pump) or short to ground in fuel pump. After service, RERUN Quick Test

XB140 CHECK POWER-TO-PUMP/FPM CIRCUIT FOR SHORT TO GROUND

Key off
IFS switch disconnected
Disconnect PCM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Install breakout box, leave PCM disconnected
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Measure resistance between Test Pin 8 and Test Pin 40 at the breakout box

Is resistance greater than 10, 000 ohms?

Yes	No
GO to XB141	SERVICE power-to-pump/FPM circuit for short to ground. REMOVE breakout box. RECONNECT all components. CLEAR Continuous Memory. START engine, WAIT 5 seconds. Key off. RERUN Quick Test

XB141 CHECK VCRM

Key off
IFS switch disconnected
Breakout box installed, PCM disconnected
Reconnect VCRM
Jumper Test Pin 22 to Test Pin 40 at the breakout box
While measuring voltage between Test Pin 8 and Test Pin 60 at the breakout box, turn key on
Key off

Was voltage greater than 8.5 volts?

Yes	No
REPLACE PCM. REMOVE breakout box. RECONNECT all components. CLEAR Continuous Memory. START engine, WAIT 5 seconds. Key off. RERUN Quick Test	REPLACE VCRM. REMOVE breakout box. RECONNECT all components. CLEAR Continuous Memory. START engine, WAIT 5 seconds. Key off. RERUN Quick Test

XB144 DOES ENGINE START AND RUN FOR ONE MINUTE WITH HIGH SPEED FUEL PUMP (HFP) RELAY DISCONNECTED?

Key off
Disconnect HFP relay (located in Power Distribution Box).
Attempt to start engine and run for one minute

Does the engine start and run for one minute?

Yes	No
RECONNECT HFP relay. GO to XB127 (to check left HO2S for short to power).	GO to XB145

XB145 CHECK FOR B(+) TO VCRM (PINS 4 AND 5)

Key off
HFP relay disconnected
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Connect DVOM negative test lead to the battery negative post
Check for voltage on Pins 4 and 5 at the VCRM vehicle harness connector

Are both voltages greater than 10.5 volts?

Yes	No
GO to XB146	SERVICE open in B(+) supply to VCRM (verify integrity of any related fuses). RECONNECT all components. RERUN Quick Test

XB146 CHECK POWER-TO-PUMP CIRCUIT CONTINUITY

Key off
HFP relay disconnected
VCRM disconnected
Measure resistance between Pin 24 of the VCRM vehicle harness connector and the power-to-pump circuit at the HFP relay vehicle harness connector

Is resistance less than 10 ohms?

Fig 9: HFP Relay Vehicle Harness Connector

Courtesy of FORD MOTOR CO.

Yes	No
REPLACE VCRM. RECONNECT all components. RERUN Quick Test	SERVICE open in power-to-pump circuit between VCRM and FPM splice. RECONNECT all components. RERUN Quick Test

XB147 CHECK POWER-TO-PUMP CIRCUIT FOR INTERMITTENT SHORT TO GROUND

Key off
Visually check the power-to-pump circuit from the VCRM to the fuel pump, the FPM circuit to the PCM and the power-to-pump circuit to the High Speed Fuel Pump (HFP) relay
Start engine
CAUTION: While performing this test, do not touch any moving/hot engine parts
Check for engine stall/stumble while performing the following test. If possible, listen for the fuel pump turning off
A fuel pressure gauge could also be installed and monitored
The VCRM FMEM will turn the fuel pump off if a short to ground is detected
- Shake, wiggle, bend the power-to-pump circuit from the VCRM to the fuel pump, PCM and HFP relay
- Lightly tap on the Inertia Fuel Shutoff Switch, Fuel Pump, HFP relay and VCRM (to simulate road shock).
Key off

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. CLEAR Continuous Memory (DTC 583 should have been set). START engine, WAIT 5 seconds. Key off. RERUN Quick Test	GO to XB148

XB148 AGAIN, CHECK POWER-TO-PUMP CIRCUIT FOR INTERMITTENT SHORT TO GROUND

Key off
Disconnect PCM, VCRM and fuel pump. Inspect each connector for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Install breakout box. Leave the PCM, VCRM and fuel pump disconnected
Connect a test lamp between Test Pin 1 (KAPWR) and Test Pin 8 (FPM)
Observe test lamp for an indication of a fault while performing the following (the light will turn on when a fault is detected, indicating a short to ground):
- Shake, wiggle, bend the power-to-pump circuit from the VCRM to the fuel pump, PCM and HFP relay
- Lightly tap on the Inertia Fuel Shutoff Switch and HFP relay (to simulate road shock).

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. REMOVE breakout box. RECONNECT all components. START engine, WAIT 5 seconds. Key off. RERUN Quick Test	Unable to isolate fault at this time. RECONNECT all components. For further diagnosis using the EEC-IV Monitor Box or Scan Tool, GO to appropriate article. For further diagnosis of this, or any other symptom, RETURN to appropriate article

XB150 CONTINUOUS MEMORY DIAGNOSTIC TROUBLE CODES (DTCS) 524/543/556: IS CONTINUOUS MEMORY DTC 583 PRESENT?

Continuous Memory DTCs 524/543 indicate that sometime during vehicle operation, when the PCM commanded the fuel pump on, voltage was not detected on the power-to-pump circuit (through FPM, PCM Pin 8). Although DTC 524 refers to the low speed output (VCRM Pin 24) and DTC 543 refers to the high speed output, it is not possible to distinguish between circuits due to the vehicle wiring and fuel pump operating strategy

Possible causes:

Open in power-to-pump circuit between the VCRM and FPM splice
Open in B(+) supply to VCRM (Pins 4 and 5).
Left HO2S short to power

Continuous Memory DTC 556 indicates that sometime during vehicle operation, a fuel pump primary circuit failure occurred.

Possible causes:

Open or short in FP circuit (PCM Pin 22).

Is Continuous Memory DTC 583 also present?

Yes	No
Continuous DTC 583 indicates that an over current (short to ground) occurred on power-to-pump/FPM circuit. This could also result in DTCs 524/543 being set. GO to XB136	GO to XB151

XB151 CHECK POWER-TO-PUMP AND FP CIRCUITS

Start engine
CAUTION: While performing this test, do not touch any moving/hot engine parts
Disconnect High Speed Fuel Pump (HFP) relay (located in power distribution box).
Connect a test lamp between the power-to-pump circuit at the HFP relay vehicle harness connector and chassis ground
Observe test lamp for an indication of a fault while performing the following: (The lamp will go out if an open or FP circuit short to power is detected. Also listen for engine stall/stumble or the fuel pump turning off. A fuel pressure gauge could also be installed and monitored.)
- For DTCs 524/543: shake, wiggle, bend the power-to-pump circuit from the VCRM to the FPM splice and the B(+) circuit to Pins 4 and 5 at the VCRM
- For DTC 556: shake, wiggle, bend the FP circuit from the VCRM to PCM
Key off
Reconnect HFP relay

Is fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. CLEAR Continuous Memor. RECONNECT all components. RERUN Quick Test	If DTC 556 was present: GO to XB152 If DTC 556 was not present: GO to XB158

XB152 CHECK FP CIRCUIT FOR INTERMITTENT SHORT TO GROUND

Key off
Disconnect PCM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Connect a DVOM between Pin 18 and Pin 1 of the VCRM vehicle harness connector
While monitoring the DVOM resistance reading for an indication of a short to ground, perform the following:
- Shake, wiggle, bend the FP circuit between the VCRM vehicle harness connector and the PCM vehicle harness connector. Also check the FP circuit to the Data Link Connector (DLC).

Is a short to ground indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. RECONNECT all components. CLEAR Continuous Memory. RERUN Quick Test	Unable to isolate fault at this time. RECONNECT all components. For further diagnosis using the EEC-IV Monitor Box or Scan Tool, GO to appropriate article. For further diagnosis of this, or any other symptom, RETURN to appropriate article.

XB155 CONTINUOUS MEMORY DIAGNOSTIC TROUBLE CODE (DTC) 542: CHECK POWER-TO-PUMP AND FUEL PUMP GROUND CIRCUITS FOR INTERMITTENT OPEN

Continuous Memory DTC 542 indicates that one of the following intermittent conditions has occurred:

Fuel pump circuit activated when PCM expected circuit to be off (ex. fuel pump prime or test procedure).
Open in the FPM, power-to-pump (FPM splice to fuel pump), fuel pump or fuel pump ground circuit
FPM or power-to-pump circuit short to power
VCRM output driver or HFP relay contacts stuck closed
HFP circuit short to ground
Left HO2S signal circuit short to power
Engine stall due to excessive load

Start engine
CAUTION: While performing this test, do not touch any moving/hot engine parts
Check for engine stall/stumble while performing the following (if possible listen for fuel pump turning off, or install and monitor a fuel pressure gauge):
- Shake, wiggle, bend the power-to-pump circuit from the fuel pump to FPM splice
- Lightly tap on the fuel pump, Inertia Fuel Shutoff switch and VCRM (to simulate road shock).
Key off

Is fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. CLEAR Continuous Memo. RERUN Quick Test	GO to XB156

XB156 CHECK FPM, POWER-TO-PUMP AND FUEL PUMP GROUND CIRCUITS FOR INTERMITTENT OPENS OR SHORTS TO POWER. CHECK HFP CIRCUIT FOR SHORT TO GND

Key off
Disconnect PCM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Install breakout box, leave PCM disconnected
Connect a test lamp between Test Pin 8 and Test Pin 37 at the breakout box
Key on, engine off
Observe test lamp for an indication of a fault while performing the following: (The light will go out if an open circuit is detected. The light will also go out, and the fuel pump will run, if a short to power or HFP circuit short to ground is detected.)
- Shake, wiggle, bend the following circuits: FPM, power-to-pump (VCRM to fuel pump, including circuit to HFP relay), fuel pump ground and HFP circuit between the HFP relay and VCRM
- Lightly tap on the Inertia Fuel Shutoff switch, HFP relay and VCRM (to simulate road shock)

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. REMOVE breakout box. RECONNECT all components. RERUN Quick Test	GO to XB158 (to check left HO2S for intermittent short to power).

XB158 CHECK LEFT HO2S CIRCUIT FOR INTERMITTENT SHORT TO POWER

NOTE: Due to the internal circuitry of the PCM, an intermittent left HO2S signal short to power could produce Continuous Memory DTCs 524, 542 or 543

Key off
Install breakout box, if applicable
Breakout box installed, PCM disconnected
Connect a test lamp between Test Pin 43 (HO2S-L) and Test Pin 40 at the breakout box
Key on
Observe test lamp for an indication of a fault while performing the following (the light will turn on bright if a fault is detected):
- Shake, wiggle, bend the left HO2S circuit from the HO2S to the PCM
- Lightly tap on the HO2S (to simulate road shock).

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. REMOVE breakout box. RECONNECT all components. RERUN Quick Test	Unable to isolate fault at this time. REMOVE breakout box. RECONNECT all components. For further diagnosis using the EEC-IV Monitor Box or Scan Tool, GO to appropriate article. For further diagnosis of this, or any other symptom, RETURN to appropriate article

XB160 LACK OF POWER/HARD START: VERIFY HIGH SPEED FUEL PUMP (HFP) OPERATION AND CHECK FOR VOLTAGE TO HFP RELAY

Key off
Disconnect HFP relay (located in Power Distribution Box).
Measure voltage between B(+) circuit at the HFP relay vehicle harness connector and the battery negative post
Key on
Measure voltage between the IGN START/RUN circuit at the HFP relay vehicle harness connector and the battery negative post.
Key off

Were both voltages greater than 10.5 volts?

Fig 10: HFP Relay Vehicle Harness Connector

Courtesy of FORD MOTOR CO.

Yes	No
GO to XB161	SERVICE open in B(+) or IGN START/RUN circuit (verify condition of related fuses). RECONNECT all components. RE-EVALUATE symptom

XB161 CHECK POWER-TO-PUMP CIRCUIT CONTINUITY BETWEEN HFP RELAY AND SPLICE

Key off
HFP relay disconnected
Measure resistance between the power-to-pump circuit at the HFP relay vehicle harness connector and the battery negative post

Is resistance less than 10.0 ohms?

Yes	No
GO to XB162	SERVICE open in power-to-pump circuit between the HFP relay and splice to main power-to-pump circuit. RECONNECT all components. RE-EVALUATE symptom

XB162 CHECK VCRM AND HFP CIRCUIT OPERATION

Key off
Reconnect HFP relay
Start and run engine to warm to normal operating temperature
Key off
Disconnect HFP relay
Connect DVOM between the B(+) circuit and the HFP circuit at the HFP relay vehicle harness connector
All accessories off (radio, A/C, etc.)
Start engine and let idle. Within 10 seconds of the start, note DVOM voltage

Does the voltage decrease at least 0.4 volts from the first reading within 2 minutes of the start?

NOTE: The HFP circuit output from the VCRM should be grounded during the initial start, but will unground within 2 minutes of the start. The exact amount of time the circuit is grounded is coolant temperature dependent

Yes	No
Key off. VCRM and HFP circuits are OK. GO to XB163 (to check HFP relay).	Key off. GO to XB165 (to check HFP circuit).

XB163 CHECK HFP RELAY OPERATION

Key off
HFP relay disconnected
Connect a jumper wire between the IGN START/RUN pin of the HFP relay (Pin 85) and the B(+) post
Connect another jumper wire to the HFP circuit of the HFP relay (Pin 86).
While connecting and disconnecting the other end of the HFP circuit jumper to the battery negative post, listen to the HFP relay

Does the HFP relay "click" when the jumper is connected and disconnected from the battery negative post?

Fig 11: HFP Relay Terminals

Courtesy of FORD MOTOR CO.

Yes	No
REMOVE jumper wires. RECONNECT HFP relay. The High Speed Fuel Pump control is working properly. RETURN to appropriate article	REMOVE jumper wires. REPLACE HFP relay. RECONNECT all components. RE-EVALUATE symptom

XB165 CHECK HFP CIRCUIT CONTINUITY

Key off
HFP relay disconnected
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Measure resistance between Pin 10 of the VCRM vehicle harness connector and the HFP circuit at the HFP relay vehicle harness connector

Is resistance less than 5.0 ohms?

Yes	No
GO to XB166	SERVICE open in HFP circuit. RECONNECT all components. RE-EVALUATE symptom

XB166 CHECK HFP CIRCUIT FOR SHORT TO POWER

Key off
HFP relay disconnected
VCRM disconnected
Key on
Measure voltage between the HFP circuit at the HFP relay vehicle harness connector and the battery negative post
Key off

Was voltage less than 1.0 volt?

Yes	No
GO to XB167	SERVICE HFP circuit short to power. RECONNECT all components. RE-EVALUATE symptom

XB167 CHECK HFP CIRCUIT FOR SHORT TO GROUND

Key off
HFP relay disconnected
VCRM disconnected
Measure resistance between the HFP circuit at the HFP relay vehicle harness connector and the battery negative post

Is resistance greater than 10, 000 ohms?

Yes	No
REPLACE VCRM. RECONNECT all components. RE-EVALUATE symptom	SERVICE HFP circuit short to ground. RECONNECT all components. RE-EVALUATE symptom

XB170 DIAGNOSTIC TROUBLE CODE (DTC) 587: CHECK WIRING HARNESS

DTC 587 indicates a Data Communications Link (DCL) error between the PCM and VCRM (DCL includes the DATA (+) and DATA (-) circuits).

Possible causes:

Open or short in DATA (+) or DATA (-) circuit
Damaged VCRM
Damaged PCM

Check vehicle harness that contains the DATA (+) and DATA (-) circuits for close proximity to high voltage wires, aftermarket modifications, etc

Yes	No
If Key On, Engine Off DTC 587 is present: GO to XB171 For Continuous Memory DTC 587 only: GO to XB180	SERVICE as necessary. CLEAR Continuous Memory. START engine. TURN A/C on, WAIT 15 seconds. A/C off. Engine off. RERUN Quick Test

XB171 CHECK DATA (+) AND DATA (-) FOR SHORT TO POWER

Key off
Disconnect any test equipment connected to the Data Link Connector (DLC) (leave equipment disconnected throughout procedure unless otherwise instructed).
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Install breakout box, leave PCM disconnected
Key on
Measure voltage between Test Pin 18 and Test Pin 40 at the breakout box
Measure voltage between Test Pin 19 and Test Pin 40 at the breakout box
Key off

Were both voltages less than 1.0 volt?

Yes	No
GO to XB172	SERVICE DATA (+) or DATA (-) circuit short to power. REMOVE breakout box. RECONNECT all components. START engine. TURN A/C on, WAIT 15 seconds. A/C off. Engine off. RERUN Quick Test

XB172 CHECK DATA (+) AND DATA (-) FOR SHORT TO GROUND OR EACH OTHER

Key off
Breakout box installed, PCM disconnected
VCRM disconnected
Measure resistance between Test Pin 18 and Test Pin 40 at the breakout box
Measure resistance between Test Pin 19 and Test Pin 40 at the breakout box
Measure resistance between Test Pin 18 and Test Pin 19 at the breakout box

Are all resistances greater than 10, 000 ohms?

Yes	No
GO to XB173	SERVICE short circuit. REMOVE breakout box. RECONNECT all components. START engine. A/C on, WAIT 15 seconds. A/C off. Engine off. RERUN Quick Test

XB173 CHECK DATA (+) AND DATA (-) CIRCUIT CONTINUITY

Key off
Breakout box installed, PCM disconnected
VCRM disconnected
Measure continuity between Test Pin 18 at the breakout box and Pin 21 at the VCRM vehicle harness connector
Measure continuity between Test Pin 19 at the breakout box and Pin 23 at the VCRM vehicle harness connector

Are both resistances less than 5.0 ohms?

Yes	No
GO to XB174	SERVICE open in DATA (+) or DATA (-) circuit. REMOVE breakout box. RECONNECT all components. START engine. TURN A/C on, WAIT 15 seconds. A/C off. Engine off. RERUN Quick Test

XB174 CHECK DCL IN VCRM

Key off
Breakout box installed, PCM disconnected
Reconnect VCRM
Key on
Measure voltage between Test Pin 18 (DATA +) and Test Pin 19 (DATA -) at the breakout box

Is voltage between 3.5 and 5.3 volts?

Yes	No
Key off. GO to XB175	Key off. REPLACE VCRM. REMOVE breakout box. RECONNECT all components. START engine. A/C on, wait 15 seconds. A/C off. Engine off. RERUN Quick Test

XB175 CHECK DATA(-) CIRCUIT IN VCRM

Key off
Breakout box installed, PCM disconnected
VCRM connected
Measure resistance between Test Pin 19 (DATA -) and Test Pin 40 (GND).

Is resistance between 1500 and 2500 ohms?

Yes	No
GO to XB176	Key off. REPLACE VCRM. REMOVE breakout box. RECONNECT all components. START engine. A/C on, wait 15 seconds. A/C off. Engine off

XB176 VERIFY THAT PCM CAN COMMUNICATE ON DCL

NOTE: The purpose of this test is to verify that the PCM can communicate on DCL. A Scan Tool (ST) is required for this test step (ex. New Generation Star (NGS)). Refer to the ST operating instructions for specific operating procedure

Key off
Remove breakout box
Reconnect PCM
Connect Scan Tool to DLC
Start engine
While in DCL display, view the RPM Parameter Identification (PID).
While monitoring RPM, change engine speed

Does the RPM PID display and can the value change?

Yes	No
Key off. GO to XB177	Key off. GO to XB179

XB177 VERIFY DCL IN VCRM

Key off
PCM connected
VCRM connected
A/C off
Enter Output State Diagnostic Test Mode (OS DTM)
Outputs off
Depress throttle (near WOT), wait until the MIL flashes once (about 10 seconds). Release throttle
Cooling fan should come on
Depress throttle to turn fan off

Does fan come on and turn off as requested during Output State check?

NOTE: The cooling fan can only be cycled once while in Output State DTM. To retest, exit and re-enter OS DTM

Yes	No
EXIT OS DTM. GO to XB178	VERIFY OS DTM is operating properly. (The MIL can be viewed and should change when the throttle is depressed and released. If the MIL does not change, check throttle linkage, DLC connections, etc.) If OS DTM is operating properly, REPLACE VCRM. RECONNECT all components. START engine. A/C on, WAIT 15 seconds. A/C off. Engine off. RERUN Quick Test

XB178 CHECK DCL IN VCRM

Key off
PCM connected
VCRM connected
Disconnect engine cooling fan
A/C off, defroster off
Perform KOEO Self-Test

Is KOEO DTC 582 present?

Yes	No
RECONNECT cooling fan. No problem is indicated at this time. The DATA (+) and DATA (-) circuits check OK, and DCL is operational in the PCM and VCRM. RETURN to appropriate article to address any other symptoms	ALLOW time for engine to cool down (to verify that the cooling fan will not attempt to come on). After engine is cooled down, start engine, wait 10 seconds, then turn engine off. RERUN KOEO Self-Test. If KOEO DTC 582 is still not present, REPLACE VCRM. RECONNECT cooling fan. START engine. A/C on, WAIT 15 seconds. A/C off. Engine off. RERUN Quick Test

XB179 CHECK DATA (+) AND DATA (-) CIRCUIT CONTINUITY TO DLC

Key off
Reinstall breakout box, leave PCM disconnected
Disconnect ST from DLC
Measure resistance between Test Pin 18 and the DATA (+) circuit (T/O) at the DLC vehicle harness connector
Measure resistance between Test Pin 19 and the DATA (-) circuit (PK/LB) at the DLC vehicle harness connector

Are both resistances less than 5.0 ohms?

Yes	No
REPLACE PCM. REMOVE breakout box. RECONNECT all components. START engine. A/C on, WAIT 15 seconds. A/C off. Engine off. RERUN Quick Test	SERVICE open circuit. RETURN to XB176 and continue as directed

XB180 CHECK DATA (+) AND DATA (-) CIRCUITS FOR INTERMITTENT CONCERNS

WARNING: WHILE PERFORMING THIS TEST STEP, THE ENGINE COOLING FAN MAY TURN ON. KEEP CLEAR OF THE ENGINE COOLING FAN

Start engine
A/C off
Engine cooling fan off. (This test is to be performed while the cooling fan is off.)
Check for cooling fan coming on (for other than normal operation) while performing the following, (the VCRM will turn the fan on if a DCL communication fault is detected):
- Shake, wiggle, bend the DATA (+) and DATA (-) circuits between the PCM and VCRM, and between the DLC and splice
- Lightly tap on the VCRM to simulate road shock

Did the cooling fan come on for other than normal operation?

Yes	No
ISOLATE fault and SERVICE as necessary. CLEAR Continuous Memory. START engine. TURN A/C on, WAIT 15 seconds. A/C off. Engine off. RERUN Quick Test	Key off. GO to XB181

XB181 CHECK DATA (+) AND DATA (-) CIRCUITS FOR INTERMITTENT SHORTS

Key off
Disconnect test equipment from DLC
Disconnect VCRM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Disconnect PCM. Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary
Install breakout box, leave PCM disconnected
Connect a jumper wire between the DATA (+) (T/O) and DATA (-) (PK/LB) circuits at the DLC
Connect a test lamp between Test Pin 19 and Test Pin 37 at the breakout box
Observe test lamp for an indication of a fault while performing the following, (the test lamp will come on when a fault is detected, indicating a short to ground):
- Shake, wiggle, bend the DATA (+) and DATA (-) circuits between the PCM and VCRM connectors and between the DLC and splice
Reconnect test lamp between Test Pin 19 and Test Pin 40 at the breakout box
Key on
Observe test lamp for an indication of a fault (test lamp will come on, indicating a short to power) while exercising the DATA (+) and DATA (-) circuits as done above
Key off
Remove jumper wire

Is a fault indicated?

Yes	No
ISOLATE fault and SERVICE as necessary. REMOVE breakout box. RECONNECT all components. START engine. TURN A/C on, WAIT 15 seconds. A/C off. Engine off. RERUN Quick Test	GO to XB182

XB182 CHECK DATA (+) AND DATA (-) CIRCUITS FOR INTERMITTENT OPENS

Key off
Breakout box installed, PCM disconnected
VCRM disconnected
Connect a jumper wire between Pin 21 and Pin 23 at the VCRM vehicle harness connector (be careful that jumper wire does not contact other pins).
Connect DVOM between Test Pin 18 and Test Pin 19 at the breakout box
While monitoring the resistance reading, shake, wiggle, bend the DATA (+) and DATA (-) circuits between the PCM and VCRM connectors

Does resistance reading go above 5.0 ohms (indicating an open)?

Yes	No
ISOLATE fault and SERVICE as necessary. REMOVE jumper wire and breakout box. RECONNECT all components. START engine. A/C on, WAIT 15 seconds. A/C off. Engine off. RERUN Quick Test	Unable to isolate fault at this time. REMOVE jumper wire and breakout box. RECONNECT all components. For further diagnosis using the EEC-IV Monitor Box or Scan Tool, GO to appropriate article. For further diagnosis of this, or any other symptom, RETURN to appropriate article