EXPERTEC Technical Service Bulletins (316528)
Publication date: 1994-02-15Reference number: 316528
EXPERTEC TECHNICAL SERVICE BULLETINS
TECHNICAL SERVICE BULLETIN
SMU - SECTION 6E3 DRIVEABILITY AND EMISSIONS
Model(s): 1993-94 Chevrolet Camaro
1993 Chevrolet Corvette
1993-94 Pontiac Firebird
with 5.7L Engine (VIN P - RPO LT1)
Bulletin No.: 316528
Date: February 15, 1994
SERVICE MANUALS AFFECTED
Section 6E3-A, DTC 36 Distributor Ignition System (Faulty High Resolution Pulse or Extra Low Resolution Pulse Detected). Use the revised DTC 36 chart (see Fig 1 and Fig 2 ) provided in place of the DTC 36 chart in these service manuals:
- 1993 Corvette Service Manual (ST-364-93-2)
- 1993 Camaro Service Manual (ST-368-93)
- 1993 Firebird Service Manual (ST-9310-F)
Section 6E3-A, Chart A-5 Fuel Pump Relay Circuit. Use the revised CHART A-5 (see Fig 5 ) and facing page provided in place of the CHART A-5 and facing page in these service manuals:
- 1993 CAMARO SERVICE MANUAL (ST-368-93)
- 1993 FIREBIRD SERVICE MANUAL (S-9310-F)
Section 6E3-A, DTC 41 Ignition Control (IC) Circuit (Open Circuit). Use the revised DTC 41 chart (see Fig 3 and Fig 4 ) and facing page provided in place of the DTC 41 chart and facing page in this service manual. The DTC 41 facing page art (MS12328) shows both possible wire colors for the High Resolution circuit (CKT430). Refer to the art provided when performing any ignition system diagnosis in this manual:
- 1994 CAMARO/FIREBIRD SERVICE MANUAL (GMP/94F-2)
CHART A-5 FUEL PUMP RELAY CIRCUIT 5.7L (VIN P) "F" CARLINE (SFI)
CIRCUIT DESCRIPTION
When the ignition switch is turned "ON," the Engine Control Module (ECM) will turn "ON" the in-tank fuel pump. It will remain "ON" as long as the ECM is receiving ignition low resolution reference pulses from the distributor ignition system.
If there are no reference pulses, the ECM will shut "OFF" the fuel pump about 2-3 seconds after key "ON."
The pump will deliver fuel to the fuel rail and injectors, then to the pressure regulator, where the system pressure is controlled to 284-325 kPa (41-47 psi). Excess fuel is then returned to the fuel tank.
When the engine is stopped, the fuel pump can be turned "ON" by using the Tech 1. Improper fuel system pressure will result in one or all of the following symptoms:
o Cranks but won't run.
o DTC 44 and 64.
o DTC 45 and 65.
o Cuts out, may feel like ignition problem.
o Poor fuel economy, loss of power.
o Hesitation.
TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
- The fuel pump relay is located under the dead pedal, (foot rest) on the driver's side of the vehicle. Checks for 12 volt supply to the fuel pump relay. Check ECM IGN fuse for being open. If fuse is open, check CKT 439 for being grounded. If ECM IGN fuse was OK, check CKT 439 for being open.
- The test light should illuminate for 2 seconds when the ignition was turned "ON."
A TECH 1 can also be used to enable the fuel pump relay control circuit.
DTC 41 IGNITION CONTROL (IC) CIRCUIT (OPEN CIRCUIT) 5.7L (VIN P) "F" CARLINE (SFI)
CIRCUIT DESCRIPTION
The distributor ignition system provides two timing inputs to the PCM, high resolution signal (360 pulses per crankshaft revolution) and low resolution signal (4 pulses per crankshaft revolution). The PCM uses these two reference pulses to determine individual ignition spark timing for each cylinder.
Once the PCM calculates ignition timing, the timing signal will be sent to the ignition coil module on the IC circuit. Each timing pulse received by the ignition coil module, on the IC circuit, will trigger the coil module to operate the ignition coil. Secondary ignition voltage is induced and is then sent to the distributor for distribution to each spark plug.
The IC signal voltage ranges from about .5 volt to 4.5 volts.
DTC 41 Will Set When: Voltage on CKT 423 exceeds 4.6 volts and engine speed is less than 1500 RPM.
Action Taken (PCM will default to): If a DTC 41 is detected, the PCM will disable the fuel injectors to prevent flooding of the engine. DTC 41 will be stored in the PCM memory but will not turn "ON" the Malfunction Indicator Lamp (MIL).
DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
- This determines if the DTC 41 is intermittent.
- This check determines if the IC signal from the PCM is available at the ignition coil driver. The IC circuit voltage should be between about .5 and 4.5 volts.
- The remaining tests begin to check that the coil driver circuitry is OK.
- If all wiring and connections are OK, check the ignition coil or the ignition coil voltage supply. Check coil fuse for being open.
Diagnostic Aids: Since the coil driver gets its power from the coil, check the ignition feed circuit to the ignition coil for opens. DTC 41 will set only during cranking.