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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 347 (Engine Controls Self-Diagnostics - 2.2L Bi-Fuel) >> Diagnostic Tests >> DTC P0300-P0304: Engine Misfire Detected >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check - Engine Controls (Alternative Fuels). If yes, go to next step. If no, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS (ALTERNATIVE FUELS)  under SELF-DIAGNOSTIC SYSTEM.
  2. Turn ignition switch to RUN position, engine OFF. Observe the DTC information using a scan tool. Are there any other DTCs set? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. Start the engine. Clear the DTCs using a scan tool. Allow the engine to reach operating temperature. Observe the MISFIRE CURRENT COUNTERS using a scan tool. Are any of the Misfire Current Counters incrementing? If yes, go to step  6. If no, go to next step.
  4. Force a switch over to gasoline using the scan tool output controls function. Observe the MISFIRE CURRENT COUNTERS using a scan tool. Are any of the Misfire Current Counters incrementing? If yes, go to DTC P0201-P0204: INJECTOR CONTROL CIRCUIT . If no, go to next step.
  5. Observe the Freeze Frame and the Failure records data for this DTC. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the conditions for running the DTC. CONDITIONS FOR RUNNING THE DTC . You may also operate the vehicle within the conditions that you observed from the Freeze Frame, and the Failure Records data. Does the DTC fail this ignition cycle? If yes, go to next step. If no, go to DIAGNOSTIC AIDS .
  6. Is the engine misfiring? If yes, go to step  8. If no, go to next step.
  7. Perform the Crankshaft Variation Learn Procedure. See CKP SYSTEM VARIATION LEARN PROCEDURE under PROGRAMMING in SELF-DIAGNOSTICS - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE - GASOLINE article. Start the engine. Observe the Misfire Current Counters using a scan tool. Are any of the Misfire Current Counters incrementing? If yes, go to BASE ENGINE MISFIRE WITHOUT INTERNAL ENGINE NOISES under SYMPTOMS in TROUBLE SHOOTING - NO CODES - 2.2L CAVALIER - BI-FUEL - CNG/GASOLINE article. If no, go to step  18.
  8. Observe the MISFIRE CURRENT COUNTERS using a scan tool. Is there only one Misfire Current Counter incrementing? If yes, go to next step. If no, go to step  18.
  9. Turn ignition switch to OFF position. Remove the Alt. Fuel (AF) Relay. Remove the fuel pump relay. Remove the ignition coil housing assembly, keeping the Ignition Control Module (ICM) assembly connected to the harness connector. Not grounding the ICM housing may cause an erratic spark. Connect a jumper wire between the top of the ICM and a good ground. Install the Ignition System Diagnosis Harness (J 36012-A), or equivalent. Install Spark Tester (J 26792), or equivalent on the No. 1 spark plug jumper wire. Ground the No. 4 spark plug jumper wire. The No. 4 wire is the companion to No. 1. Crank the engine with the remaining spark plug wires connected. Repeat the procedure by installing the spark tester on No. 4 and grounding No. 1. Do the same for the No. 2 and the No. 3 spark plugs. Ensure the companion wire is grounded. Does the spark tester spark on all cylinders? If yes, go to next step. If no, go to ELECTRONIC IGNITION SYSTEM DIAGNOSIS WITHOUT SPECIAL TOOL or ELECTRONIC IGNITION SYSTEM DIAGNOSIS WITH SPECIAL TOOL under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTS - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article.
  10. Remove the spark plug from the cylinder that indicates a misfire. If the spark plug is gas, coolant, or oil fouled, determine the cause of the fouling. See appropriate article in ENGINES. Inspect the spark plug. See SPARK PLUG INSPECTION under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTS - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article. Did you find and correct the condition? If yes, go to step  15. If no, go to next step.
  11. Swap the suspected spark plug with another cylinder that is operating correctly. Start the engine. Operate the engine within the conditions that the misfire occurred. Monitor the MISFIRE CURRENT COUNTERS using a scan tool. Did the misfire move with the spark plug? If yes, go to step  15. If no, go to next step.
    12. NOTE: Ensure all the injectors operate. High resistance in an injector circuit causes the injector to be inoperative without setting a fuel injector DTC. Return to this diagnostic after you complete the Fuel Injector Coil Test.
  12. Perform the Fuel Injector Coil Test. See FUEL INJECTOR COIL TEST under FUEL SYSTEMS (CNG) in SYSTEM & COMPONENT TESTS - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article. Did you find and correct the condition? If yes, go to step  16. If no, go to next step.
  13. Perform the Fuel System Diagnosis. See FUEL SYSTEM DIAGNOSIS (CNG) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article. Did you find and correct the condition? If yes, go to step  16. If no, diagnose base engine components for cause of misfire. Go to BASE ENGINE MISFIRE WITHOUT INTERNAL ENGINE NOISES under SYMPTOMS in TROUBLE SHOOTING - NO CODES - 2.2L CAVALIER - BI-FUEL - CNG/GASOLINE article.
  14. Check or test for the following conditions:
    • Check the vacuum hoses for splits, kinks, and the correct connections.
    • Check for vacuum leaks at the throttle body and at the intake manifold.
    • Check the PCM grounds for being clean, tight, and in the correct location.
    • Check for the correct fuel pressure. See FUEL PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article.
    • Inspect for fouled or damaged spark plugs. See SPARK PLUG INSPECTION under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTS - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article.
    • Inspect the exhaust system for restrictions. See RESTRICTED EXHAUST under SYMPTOM TESTS in TROUBLE SHOOTING - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE - GASOLINE article.

    Did you find and correct the condition? If yes, go to step  16. If no, go to appropriate article in ENGINES.

  15. Replace the spark plug. After repair, go to next step.
  16. Was the customers concern that the was MIL flashing? If yes, go to next step. If no, go to step  18.
  17. Operate the vehicle at 2500 RPM for 4 minutes. Operate the vehicle within the Conditions for Running the DTC P0420 as specified in the supporting text. See CONDITIONS FOR RUNNING DTC under DTC P0420: TWC SYSTEM - LOW EFFICIENCY under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE - GASOLINE article. Does the DTC run and pass? If yes, go to next. If no, see DTC P0420: TWC SYSTEM - LOW EFFICIENCY under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE - GASOLINE article.
  18. Clear the DTCs using a scan tool. Turn ignition switch to OFF position for 30 seconds. Turn ignition switch to RUN position, engine OFF. Operate the vehicle within the Conditions for Running the DTC. See 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? If yes, go to step  2. If no, go to next step.
  19. Observe the CAPTURE INFO using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
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