Diagnostic Procedure
- If diagnostic system check has already been performed, go to next step. If diagnostic system check has not been performed, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article.
- Turn ignition switch to RUN position, engine off. Observe DTC information using a scan tool. Is DTC P0101, P0123, P0230, P0336, P0341, P0601, P0602, P1626, P1629, P1631 or P2610 set? If yes, diagnose affected DTC(s). See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article. If no, go to next step.
- Attempt to start the engine. Observe the engine speed parameter using a scan tool, while the engine is cranking. Does the engine speed parameter display cranking RPM? If yes, go to next step. If no, go to ELECTRONIC IGNITION SYSTEM DIAGNOSIS under IGNITION SYSTEMS.
- Command the fuel pump relay ON using a scan tool. Does the fuel pump turn ON? On all models, if yes, go to next step. On Bonneville and LeSabre, if no, go to FUEL SYSTEM DIAGNOSIS . On Park Avenue, if no, go to FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS (PARK AVENUE) under FUEL SYSTEMS.
- Turn ignition switch to OFF position. Disconnect a spark plug wire. Install the Spark Tester (J 26792), or equivalent, to the spark plug wire. Attempt to start the engine. Does the spark tester spark? If yes, go to next step. If no, go to ELECTRONIC IGNITION SYSTEM DIAGNOSIS under IGNITION SYSTEMS.
- Turn ignition switch to OFF position. Disconnect a fuel injector harness connector. Install Fuel Injector Test Light (J 34730-405), or equivalent, to the fuel injector harness connector. Attempt to start the engine. Does the test light blink while the engine is cranking? If yes, go to next step. On Bonneville and LeSabre, if no, go to DTC P0341: CAMSHAFT POSITION SENSOR PERFORMANCE in SELF-DIAGNOSTICS - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article. On Park Avenue, go to FUEL INJECTOR CIRCUIT DIAGNOSIS under FUEL SYSTEMS.
- Turn ignition switch to OFF position. Install Fuel Pressure Gauge (J 34730-1A), or equivalent. See Figure. Turn ignition switch to RUN position, engine OFF. Command the fuel pump relay ON using a scan tool. On Bonneville and LeSabre, is the fuel pressure 48-54 psi (334-375 kPa) or, on Park Avenue, is the fuel pressure 53-59 psi (364-405 kPa), while the fuel pump is operating? If yes, go to next step. If no, go to FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS.
- Check for the following conditions:
- Collapsed air intake duct.
- Restricted air filter element.
- Fouled spark plugs. If the spark plugs are fouled, determine what caused the condition.
- Engine mechanical condition (worn timing chain and gears, low compression, etc.). See appropriate article in ENGINES.
- Restricted exhaust system. See RESTRICTED EXHAUST under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article.
- Faulty Engine Coolant Temperature (ECT) sensor. See ENGINE COOLANT TEMPERATURE SENSOR under SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article.
- Faulty Manifold Absolute Pressure (MAP) sensor. See MANIFOLD ABSOLUTE PRESSURE SENSOR under SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article.
- Stuck Throttle Position (TP) sensor. See DTC P0121: TP SENSOR PERFORMANCE under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article.
After completing the actions, go to next step.
- Clear the DTCs using a scan tool. Attempt to start the engine. Does the engine start and continue to operate? If yes, go to next step. If no, go to step 2.
- Idle the engine. Allow the engine to reach operating temperature. Observe the DTC information using a scan tool. Are any DTCs displayed? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 3.8L BONNEVILLE, GRAND PRIX, IMPALA, LESABRE, MONTE CARLO, PARK AVENUE & REGAL article. If no, system is okay at this time.