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Home › Isuzu › 2006 › Ascender Limited, RWD › Repair and Diagnosis › Engine Performance › System › Engine Control System - 5.3L - DTC P0449 To P1516 › DTC P0641 › Test Description

Test Description

The number below refers to the step number on the diagnostic table.

  1. 9:  A short to voltage on the signal circuit of the MAP and FTP sensors may backfeed through the sensor into the 5-volt reference circuit and set this DTC.
DTC P0641

Step Action Values Yes No
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Connector End Views or Engine Control Module (ECM) Connector End Views
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Does the DTC fail this ignition?		 - Go to Step 3  Go to Testing for Intermittent Conditions and Poor Connections
3
  1. Turn OFF the ignition.
  2. Disconnect the engine oil pressure (EOP) sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the 5-volt reference circuit of the EOP sensor to a good ground with a DMM. Refer to Circuit Testing .
Is the voltage within the specified range?		 4.8-5.2 V Go to Step 4  Go to Step 5 
4
  1. Connect the EOP sensor.
  2. Disconnect the manifold absolute pressure (MAP) sensor.
  3. Measure the voltage from the 5-volt reference circuit of the MAP sensor to a good ground with a DMM. Refer to Circuit Testing .
Is the voltage within the specified range?		 4.8-5.2 V Go to Testing for Intermittent Conditions and Poor Connections Go to Step 10 
5 Is the voltage measured in step 3 more than the specified value? 5.2 V Go to Step 8  Go to Step 6 
6
  1. Monitor the DMM while disconnecting all other sensors connected to this 5-volt reference bus, one at a time.
  2. Replace the component if the voltage returns to within the specified range when one of the above components is disconnected. Refer to the appropriate replacement procedure.
Was a component replaced?		 4.8-5.2 V Go to Step 12  Go to Step 7 
7 Test the 5-volt reference circuits of all the sensors connected to this 5-volt reference bus for a short to ground or any sensor low reference circuit. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 12  Go to Step 11 
8
IMPORTANT: If a short to voltage occurs, the A/C refrigerant pressure sensor may be damaged.
Test the 5-volt reference circuits of all the sensors connected to this 5-volt reference bus for a short to voltage. Refer to Circuit Testing and Wiring Repairs .Did you find and correct the condition?		 - Go to Step 12  Go to Step 9 
9 
IMPORTANT: If a short to voltage occurs on the MAP sensor signal circuit or fuel tank pressure (FTP) sensor signal circuit, the sensors may be damaged.
Test the MAP sensor signal circuit and FTP sensor signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs .Did you find and correct the condition?		 - Go to Step 12  Go to Step 11 
10 Replace the EOP sensor. Refer to Engine Oil Pressure Sensor and/or Switch Replacement .
Did you complete the replacement?		 - Go to Step 12  -
11 Replace the engine control module (ECM). Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 - Go to Step 12  -
12
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 - Go to Step 2  Go to Step 13 
13 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List - Vehicle System OK
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