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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 330 (Engine Controls - Self-Diagnostics - 3.0L) >> Diagnostic Tests >> DTC P0301-P0306: Specific Cylinder Misfire Detected >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Saturn Vue. 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, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS .
  2. Start and allow 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, go to DIAGNOSTIC AIDS .
  3. Are any other DTCs set? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  4. Can any abnormal engine noise be heard? If yes, diagnose for an engine mechanical problem. If no, go to next step.
  5. Are there multiple misfires indicated on only one bank? If yes, diagnose ignition system. Refer to ELECTRONIC IGNITION SYSTEM (3.0L) under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L & 3.0L VUE article. If no, go to next step.
  6. Are there 2 cylinders misfiring on only one bank? If yes, diagnose for an engine mechanical problem. If no, go to next step.
  7. Inspect vacuum hoses and seals for splits, restrictions, and improper connections. Check throttle body and intake manifold for vacuum leaks, or crankcase ventilation system for vacuum leaks. Check ECM grounds for corrosion and loose connections, exhaust system for restrictions, or fuel for contamination. Did you find and correct the condition? If yes, go to step  9. If no, go to next step.
  8. Perform fuel system diagnosis. Refer to FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L & 3.0L VUE article. Did you find and correct the condition? If yes, go to next step. If no, diagnose of an engine mechanical problem.
  9. Was the customer's concern about the Malfunction Indicator Light (MIL) flashing? If yes, go to next step. If no, go to step  11.
  10. Operate the vehicle at 2500 RPM for 4 minutes. Operate the vehicle within the Conditions for Running the DTC P0421 or P0430. Refer to DTC P0421 OR P0431: WARM-UP CATALYST - BELOW THRESHOLD . Does the DTC run and pass? If yes, go to next step. If no, go to DTC P0421 OR P0431: WARM-UP CATALYST - BELOW THRESHOLD .
  11. Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING 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.
  12. Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? If yes, diagnose affected DTC(s). See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are displayed, system is okay.
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