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Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Isuzu Trooper. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform ON-BOARD DIAGNOSTIC II SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD-II system check, go to next step.
  2. Turn ignition on. Review and record scan tool FAILURE RECORDS data. Operate vehicle within FAILURE RECORDS conditions noted. On scan tool, monitor DTC information. If scan tool indicates DTC P0325 FAILED THIS IGNITION, go to next step. If scan tool display is not as specified, go to DIAGNOSTIC AIDS .
  3. Turn ignition off. Disconnect ISM 10-pin harness connector E-16. ISM is located on top of intake manifold. Disconnect PCM Blue 80-pin harness connector E-21. PCM is located at right rear of engine compartment. Go to next step.
  4. Check for open or short in Red wire between ISM harness connector E-16 terminal No. 5 and PCM harness connector E-21 terminal No. 68. See Fig 1. For PCM terminal identification, see PIN VOLTAGE CHARTS article. If problem was found, repair as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem with wiring was found, go to next step.
  5. Disconnect individual ignition coil harness connectors, and go to next step.
  6. Check wiring harness between ignition coils and ISM harness connector. If problem was found, repair as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem was found, go to next step.
  7. Check ignition coil for cracks or carbon tracking. Check ignition coil harness connectors and related wiring. Check ignition coil ground connection to be clean and tight. Ignition coil ground point is forward of the 2 ground points located on left side of intake manifold. If problem was found, repair as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem was found, go to next step.
  8. If ignition coil tested bad, replace ignition coil. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem is found, go to next step.
  9. Check ISM ground circuit for loose or poor connection. Ground point is forward of the 2 ground points located on left side of intake manifold. If problem was found, repair as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem was found, go to step  11.
  10. Repair any problem with ignition coil or ISM wiring harness. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem was found, go to next step.
  11. Replace ISM. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If problem is still present, go to next step.
  12. Replace and reprogram PCM. See POWERTRAIN CONTROL MODULE REPLACEMENT  under POWERTRAIN CONTROL MODULE. Use scan tool to clear DTC and verify repair.
Fig 1: Identifying ION Sensing Module Harness Connector E-16 Terminals
G00077229Courtesy of ISUZU MOTOR CO.
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