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Home >> Chevrolet >> 2001 >> Camaro Base, 2D Convertible, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 62 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0300-P0308: Engine Misfire Detected >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Cadillac Seville and 2003 Cadillac DeVille. 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 Crankshaft Position (CKP) system variation learn procedure before proceeding with this diagnostic table. See CRANKSHAFT POSITION SYSTEM VARIATION LEARN PROCEDURE  under PROGRAMMING.
  2. Start the engine. Allow the engine to idle or operate within the conditions listed in the Freeze Frame/Failure Records. Monitor all of the Misfire counters with the scan tool. Are any of the Misfire Current counters incrementing? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  3. Are any other DTCs set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  4. Can any abnormal engine noise be heard? If yes, see appropriate article in ENGINES. If no, go to next step.
  5. Does the scan tool indicate that the HO2S bank 1 sensor 1 or HO2S bank 2 sensor 1 voltage parameters are below 200 mV? If yes, see DTC P0131 & P0151: HO2S BANK 1 & 2, SENSOR 1 CIRCUIT - LOW VOLTAGE . If no, go to next step.
  6. Does the scan tool indicate that the HO2S bank 1 sensor 1 or HO2S bank 2 sensor 1 voltage parameters are fixed above 900 mV? If yes, see DTC P0132 & P0152: HO2S BANK 1 & 2, SENSOR 1 CIRCUIT - HIGH VOLTAGE . If no, go to next step.
  7. Inspect the following components:
    • The vacuum hoses and seals for splits, restrictions, and improper connections.
    • The throttle body and intake manifold for vacuum leaks.
    • The Exhaust Gas Recirculation (EGR) system components for vacuum leaks or excessive flow.
    • The crankcase ventilation system for vacuum leaks.
    • The PCM grounds for corrosion and loose connections.
    • The exhaust system for restrictions.
    • The fuel for contamination.

    Did you find and correct the condition? If yes, go to step  19. If no, go to next step.

    8. NOTE: DO NOT remove the connector from the Ignition Control (IC) module assembly. Not grounding the IC module assembly may cause erratic spark.
  8. Turn ignition off. Remove the fuel pump relay. Remove the affected IC module assembly. See IGNITION CONTROL MODULE under IGNITION SYSTEMS in REMOVAL & INSTALLATION - DEVILLE & SEVILLE article. Connect a jumper wire between the IC module assembly and a good ground. Install the Ignition System Diagnosis Harness. Install Spark Tester on the affected cylinder spark plug jumper wire. Crank the engine with the remaining spark plug jumper wires connected. Does the Spark Tester spark? If yes, go to step  10. If no, go to next step.
  9. Inspect the affected cylinder spark plug boot for missing or damaged ignition coil spring. Did you find and correct the condition? If yes, go to step  19. If no, see IGNITION SYSTEMS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
  10. Remove the spark plug from the cylinder that indicated a misfire. Inspect the spark plug. Does the spark plug appear to be okay? If yes, go to next step. If no, go to step  12.
  11. Exchange 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  18. If no, go to step  15.
  12. Is the spark plug oil or coolant fouled? If yes, see appropriate article in ENGINES. If no, go to next step.
  13. Is the spark plug gas fouled? If yes, go to step  16. If no, go to next step.
  14. Does the spark plug show any signs of being cracked, worn, or improperly gapped? If yes, go to step  17. If no, go to next step.
  15. Perform the fuel injector coil test. See appropriate SYSTEM & COMPONENT TESTING article. Did you find and correct the condition? If yes, go to step  19. If no, see appropriate article in ENGINES.
  16. Perform the fuel system diagnosis. See FUEL SYSTEMS in appropriate BASIC DIAGNOSTIC PROCEDURES article. Did you find and correct the condition? If yes, go to step  19. If no, see appropriate article in ENGINES.
  17. Replace or gap the spark plug. Did you complete the action? If yes, go to step  19.
  18. Replace the faulty spark plug. Did you complete the replacement? If yes, go to next step.
  19. Was the customer concern the MIL flashing? If yes, go to next step. If no, go to step  22.
  20. Operate the vehicle at 2500 RPM for 4 minutes. Operate the vehicle within the Conditions For Running DTC P0420 as specified in the supporting text. See DTC P0420: TWC SYSTEM - LOW EFFICIENCY . Does the DTC run and pass? If yes, go to next step. If no, see DTC P0420: TWC SYSTEM - LOW EFFICIENCY .
  21. Clear the DTCs with a scan tool. Turn off the ignition for 30 seconds. Start the engine and operate vehicle within the Conditions For Running DTC. You may also operate vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition cycle? If yes, go to step  2. If no, go to next step.
  22. Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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