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Home >> Chevrolet >> 2001 >> Camaro Base, 2D Convertible, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 40 (Engine Control System Self-Diagnostics - 5.7L) >> Diagnostic Tests >> DTC P0300-P0308: Engine Misfire Detected >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Pontiac Firebird and 2002 Chevrolet Camaro. 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? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
    2. NOTE: You must perform the CKP System Variation Learn Procedure before proceeding with this diagnostic table. See CRANKSHAFT POSITION SENSOR  under PROGRAMMING. Before you proceed with this diagnostic, ensure that the ABS system and the Traction Control system are functioning properly. If any DTCs, other than P0135 and P0155 are set, see DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  2. Use the scan tool in order to monitor all the Misfire Current Counters on the misfire data list. There are 8 counters, with one counter per cylinder. Are any of the Misfire Current Counters incrementing? If yes, go to step  4. If no, go to next step.
  3. Turn ON the ignition, with the engine OFF. Review the Freeze Frame/Failure Records data for this DTC, and observe the parameters. Turn OFF the ignition for 15 seconds. Start the engine. Operate the vehicle within the conditions required for this diagnostic to run. Attempt to duplicate the conditions recorded in the Freeze Frame/Failure Records. Special operating conditions that you must meet before the PCM will run this diagnostic, where applicable, are listed in Conditions for Running DTC. Select the Diagnostic Trouble Code (DTC) option. Does the scan tool indicate that this diagnostic failed this ignition cycle? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  4. Is only one Misfire Counter incrementing? If yes, go to step  6. If no, go to next step.
  5. Inspect the following items:
    • Observe the HO2S readings on the scan tool. If the signal is fixed below 200 mV, see DTC P0131 & P0151: HO2S CIRCUIT - LOW VOLTAGE - BANK 1 & 2, SENSOR 1 . If the signal is fixed above 900 mV, see DTC P0132 & P0152: HO2S CIRCUIT - HIGH VOLTAGE - BANK 1 & 2, SENSOR 1 .
    • Inspect the accessory drive belt and the pulleys for damage or misalignment.
    • Inspect the vacuum hoses for splits, for kinks, and for correct connections.
    • Inspect the throttle body and the intake manifold for vacuum leaks.
    • Inspect the crankcase ventilation valve and/or system for vacuum leaks.
    • Inspect the PCM grounds for being clean and secure.
    • Verify that all injector harness connectors are connected to the proper injector and/or cylinder.
    • Inspect the injector and the Ignition Control fuses for being open. If you find an open fuse, locate and repair the shorted circuit.
    • Test for low fuel pressure or for restricted fuel flow. See appropriate BASIC DIAGNOSTIC PROCEDURES article.
    • Inspect for a restricted exhaust.
    • Inspect for fuel contamination.

    Did any of the tests isolate a condition requiring a repair? If yes, go to step  17. If no, go to next step.

  6. Turn OFF the ignition. Disconnect the injector that corresponds to any Misfire Current Counter that was incrementing. Connect the J 34730-2C injector test lamp to the injector electrical connector. Idle the engine. Is the injector test lamp flashing? If yes, go to next step. If no, see DTC P0200: FUEL INJECTOR CONTROL CIRCUIT .
  7. Turn OFF the ignition. Reconnect the injector harness electrical connector. Disconnect the ignition wires from any spark plug that corresponds to any Misfire Current Counter that is incrementing. Install J 26792 spark tester to ground. Start the engine. Does the spark jump the tester gap, and is the spark consistent? If yes, go to step  9. If no, go to next step.
  8. Remove the ignition wire for the cylinder that is misfiring. Use the Digital Multimeter (DMM) in order to measure the resistance of the ignition wire. Is the ignition wire resistance less than 700 ohms? If yes, diagnose electronic ignition system. See appropriate SYSTEM & COMPONENT TESTING article. If no, go to step  16.
  9. Remove the spark plugs from the cylinder that indicated a misfire. Inspect the spark plugs. Does the spark plug appear to be okay? If yes, go to next step. If no, go to step  11.
    10. NOTE: If the Injector Coil Test Procedure does not isolate the condition, diagnose engine mechanical problem. See appropriate article in ENGINES.
  10. Swap the suspected spark plug with another cylinder that is operating properly. Operate the vehicle under the same conditions that the misfire occurred. Did the misfire move with the spark plug? If yes, go to step  15. If no, test fuel injector coil. See appropriate SYSTEM & COMPONENT TESTING article.
  11. Are the spark plugs oil or coolant fouled? If yes, repair engine mechanical problem. See appropriate article in ENGINES. If no, go to next step.
    12. NOTE: If the Fuel System is okay, repair engine mechanical problem. See appropriate article in ENGINES.
  12. Are the spark plugs gas-fouled? If yes, diagnose fuel system. See appropriate SYSTEM & COMPONENT TESTING article. If no, go to next step.
    13. NOTE: If the Injector Coil Test Procedure does not isolate the condition, repair engine mechanical problem. See appropriate article in ENGINES.
  13. Do the spark plugs show any signs of being cracked, worn, or improperly gapped? If yes, go to next step. If no, perform fuel injector coil test. See appropriate SYSTEM & COMPONENT TESTING article.
  14. Replace or re-gap spark plugs. If improper gap is found, be sure to re-gap spark plugs using a wire type gauge. After repairs, go to step  17.
  15. Replace the faulty spark plugs. After repairs, go to step  17.
  16. Replace the faulty ignition wires. After repairs, go to next step.
  17. Was the customer's concern that the MIL was flashing? If yes, see DTC P0420 & P0430: TWC SYSTEM - LOW EFFICIENCY - BANK 1 & 2 . If no, go to next step.
  18. Select DTC, then select the Clear DTC Information function on the scan tool. Start the engine. Allow the engine to idle until the engine reaches the normal operating temperature. Select DTC, then select the Specific DTC function. Enter the DTC number which was set. Operate the vehicle within the Conditions for Setting this DTC until the scan tool indicates the diagnostic Ran. Does the scan tool indicate that the diagnostic Passed? If yes, go to next step. If no, go to step  2.
  19. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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