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Home >> Isuzu >> 2002 >> Trooper LS, 4WD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0301: Cylinder No. 1 Misfire Detected, DTC P0302: Cylinder No. 2 Misfire Detected, DTC P0303: Cylinder No. 3 Misfire Detected, DTC P0304: Cylinder No. 4 Misfire Detected, DTC P0305: Cylinder No. 5 Misfire Detected &/Or DTC P0306: Cylinder No. 6 Misfire Detected >> Diagnostic Procedure

Diagnostic Procedure

  1. Perform ON-BOARD DIAGNOSTIC II SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD-II system check, go to next step.
  2. Start engine and run at idle. Using scan tool, read and record FREEZE FRAME data. Operate vehicle within FAILURE RECORDS conditions. On scan tool, observe MISFIRE CUR. # (1-6) display for appropriate cylinder. If MISFIRE CUR. # increases (indicating an occurring misfire) for affected cylinder, go to step  4. If MISFIRE CUR. # does not increase, go to next step.
  3. On scan tool, monitor MISFIRE HIST. # while operating vehicle within CODE ENABLE CRITERIA . If MISFIRE HIST. # increases, go to next step. If MISFIRE HIST. # does not increase, check for an intermittent problem. See DIAGNOSTIC AIDS .
  4. Check vacuum hoses for splits, kinks or improper connections. Check intake manifold for vacuum leak. If a problem is found, repair as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem is found, go to next step.
  5. Install spark tester at spark plug end of ignition coil on suspect cylinder. Crank engine. If a strong Blue spark is present, go to step  8. If no spark or weak spark is present, go to next step.
  6. Remove ignition coil related to misfiring cylinder. Check ignition coil for cracks or carbon tracking. If a problem is found, replace damaged ignition coil. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem is found, go to next step.
    7. NOTE: Ignition coil control module is part of ION sensing module system.
  7. Measure primary coil resistance. Resistance should be 2.6-2.7 k/ohms. If resistance is not as specified, replace ignition coil. If resistance is as specified, replace ignition control module. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM.
  8. Remove spark plug associated with misfiring cylinder. Check spark plug for excessive fouling. If spark plug is excessively fouled, diagnose and repair mechanical engine problem. If spark plug is not excessively fouled, go to next step.
  9. Check spark plug insulator for cracks, carbon tracking or other damage. If a problem is found, replace faulty spark plug. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem is found, go to next step.
  10. Perform FUEL INJECTOR BALANCE TEST under FUEL SYSTEM in SYSTEM & COMPONENT TESTING article. If a problem is found, repair as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem is found, go to next step.
  11. Inspect injector "O" rings for vacuum leaks. If a problem is found, repair as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem is found, go to next step.
  12. Diagnose mechanical engine problems such as faulty camshaft, leaking or sticking valves, excessive carbon deposits, weak valve springs, damaged piston rings, loose or worn rocker arms, incorrect valve timing, leaking head gasket or loose or broken motor mounts. If a problem is found, repair as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problems are found, check for an intermittent problem. See DIAGNOSTIC AIDS .
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