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Home >> Chevrolet >> 2001 >> Camaro Base, 2D Convertible, Automatic >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Control System Self-Diagnostics - 3.8L >> Diagnostic Tests >> DTC P0300-P0306: Engine Misfire Detected >> Diagnostic Procedures

Diagnostic Procedures

  1. If powertrain diagnostic system check was performed, go to next step. If powertrain diagnostic system check was not performed, go to POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under DIAGNOSTIC SYSTEM CHECKS. After performing powertrain diagnostic system check, go to next step.
  2. If any DTCs other than P0135 and P0155 are set, repair those DTCs first. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no additional DTCs are set, go to next step.
  3. Start and operate engine at idle. Operate vehicle within parameters to set DTC as recorded in FREEZE FRAME/FAILURE RECORDS. Using scan tool, select MISFIRE DATA LIST function and monitor MISFIRE CUR. COUNTERS (one counter per cylinder). If any misfire counter is incrementing, go to next step. If misfire counter is not incrementing, go to DIAGNOSTIC AIDS .
  4. Select MISFIRE HISTORY CYL # on scan tool. If misfire history displays a large value for more than one cylinder, go to next step. If misfire history does not display a large value for more than one cylinder, go to step  13.
  5. Check for split, damaged or misrouted vacuum hoses. Repair as necessary. After repairs, go to step  25. If vacuum hoses are okay, go to next step.
  6. Check for damaged or improperly installed crankcase ventilation system. Repair as necessary. After repairs, go to step  25. If vacuum hoses are okay, go to next step.
  7. Check for blockage or damage of throttle body inlet screen. Repair as necessary. After repairs, go to step  25. If vacuum hoses are okay, go to next step.
  8. Test fuel pressure. See appropriate BASIC DIAGNOSTIC PROCEDURES article. If fuel pressure tests okay, go to next step. If fuel pressure is not as specified, repair as necessary. After repairs, go to step  25.
  9. Check for contamination of fuel by water, alcohol or other foreign matter. Repair as necessary. After repairs, go to step  25. If fuel is okay, go to next step.
  10. Visually check for poor PCM or engine ground connections. See Figure. Repair as necessary. After repairs, go to step  25. If ground connections are okay, go to next step.
  11. Check for vacuum leaks at intake manifold, EGR adapter, EGR valve, EGR feed pipes or fuel injector "O" rings. Repair as necessary. After repairs, go to step  25. If no vacuum leaks are found, go to next step.
  12. Remove EGR valve. Check that EGR valve pintle is not sticking in closed or open position. Check for excessive carbon deposits or burrs that may be preventing EGR valve from closing completely. Repair or replace EGR valve as necessary. After repairs, go to step  25. If EGR valve is okay, go to next step.
  13. Perform fuel injector coil test on suspect cylinder. See appropriate SYSTEM & COMPONENT TESTING article. Replace injectors as necessary. After repairs, go to step  25. If fuel injector is okay, go to next step.
  14. Check spark plug wire on suspect cylinder for damage. Replace plug wire as necessary. After repairs, go to step  25. If spark plug wire is okay, go to next step.
  15. Install Spark Tester (J 26792) to spark plug end of spark plug wire on suspect cylinder. Jumper companion cylinder spark plug end of spark plug wire to ground. Companion cylinder is spark plug wire that shares the same ignition coil (1/4, 2/5 and 3/6). Crank engine while observing spark tester. If spark is present, go to step  20. If spark is not present, go to next step.
  16. Remove spark plug wires from ignition coils and check for carbon tracking. If carbon tracking is present, replace ignition coil and spark plug wire. After repairs, go to step  25. If carbon tracking is not present, check spark plug wire on suspect cylinder for damage. Replace plug wire as necessary. After repairs, go to step  25. If spark plug wire is okay, go to next step.
  17. Using DVOM, measure resistance of suspect spark plug wire. Specification is 3000 ohms per ft, 250 ohms per INCH of spark plug wire. Measure length of spark plug wire. If resistance is as specified for length of wire, go to next step. If resistance is not as specified for length of spark plug wire, replace plug wire as necessary. After repairs, go to step  25.
  18. Inspect suspect ignition coil for cracks, carbon tracking or damage. Replace as necessary. After repairs, go to step  25. If ignition coils are okay, go to next step.
  19. Using DVOM, measure ignition coil secondary resistance. If resistance is 5-8 K/ohms, go to step  24. If resistance is not 5-8 K/ohms, replace suspect ignition coil. After repairs, go to step  25.
  20. Remove and inspect spark plug(s) for suspect cylinder for excessive fouling. If spark plug is excessively fouled, diagnose and repair engine mechanical condition. See appropriate article in ENGINES. If spark plug(s) is okay, go to next step.
  21. Check suspect spark plug(s) insulators for cracks or carbon fouling. Check that electrode gap is 0.060" (1.52 mm). Repair or replace spark plug(s) as necessary. After repairs, go to step  25. If spark plugs are okay, go to next step.
  22. Check for engine mechanical condition. See appropriate article in ENGINES. Repair as necessary. After repairs, go to step  25. If engine mechanical condition is okay, go to next step.
  23. Check for malfunctioning transmission Torque Converter Clutch (TCC). Repair as necessary. After repairs, go to step  25. If TCC is okay, go to DIAGNOSTIC AIDS .
  24. Replace ignition control module. See REMOVAL, OVERHAUL & INSTALLATION - CARS article. After repairs, go to step  25.
  25. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine and allow it to reach normal operating temperature. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, go to step  2.
  26. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no undiagnosed DTCs are displayed, system is okay.
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