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Diagnostic Procedures

WARNING: This page is about a different car, the 2000 Isuzu Hombre. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform On-Board Diagnostic II (OBD-II) system check. See ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK in SELF-DIAGNOSTICS - INTRODUCTION article. After performing OBD-II system check, go to next step.
  2. Install Tech 2 scan tool. If DTC P0200 is also set, diagnose that DTC before proceeding. See DTC P0200: INJECTOR CONTROL CIRCUIT . If DTC P0200 is not set, go to next step.
  3. Perform a visual inspection and check vacuum hoses for splits, kinks and proper routing. Check for leaks at throttle body, intake manifold, EGR valve and PCV system. Check PCM grounds for proper connection. Check injector harness connectors for proper installation. Repair as necessary. After repairs, go to step  30. If no problems are found, go to next step.
  4. Start and allow engine to idle. Using scan tool, select MISFIRE DATA LIST function and monitor MISFIRE CURRENT counters (one counter per cylinder). If any MISFIRE CURRENT counters are incrementing, go to next step. If not, go to step  6.
  5. If all counters are equal (within a percentage of each other), go to step  7. If not, go to step  10.
  6. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data, and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. If any of MISFIRE CURRENT counters are incrementing, go to step  5. If MISFIRE CURRENT counters are not incrementing, see DIAGNOSTIC AIDS .
  7. Turn ignition off. Install fuel pressure gauge. Start engine and allow it to idle. If fuel pressure is 41-47 psi (2.9-3.3 kg/cm2 ), go to next step. If fuel pressure is not 41-47 psi (2.9-3.3 kg/cm2 ), see FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article.
  8. Check for fuel contamination. If fuel is contaminated, go to step  9. If fuel is not contaminated, go to next step.
  9. Replace contaminated fuel. After repair, go to step  30.
  10. Turn ignition off. Disconnect fuel injector harness connector. Temporarily remove ignition coil and Ignition Control Module (ICM) assembly. Install Spark Plug Jumper Wires (J-36012). Install Spark Tester (J-26792) to spark plug jumper for each cylinder, one at a time. Disconnect spark plug boot from companion cylinder at ignition coil housing and install a jumper wire between ground and spark plug connector at ignition coil housing (1-4 or 2-3). Crank engine and check for spark. If spark is present at all cylinders, go to next step. If spark is not present at one or more cylinders, go to step  20.
  11. Check for faulty spark plugs. Replace defective spark plug(s) as necessary. After repairs, go to step  30. If spark plugs are okay, go to next step.
  12. Turn ignition off. Disconnect fuel injector connectors from injectors. Install an injector test light on injector harness connector for cylinders that had misfired. Crank engine and note test light. If injector test light blinks, go to next step. If injector test light does not blink, go to step  15.
  13. Perform fuel injector test. See SYSTEM & COMPONENT TESTING article. If injectors are okay, go to next step. If injectors are not okay, go to step  16.
  14. Check for a basic engine problem (compression, cam timing, throttle body leak, restricted airflow, etc.). Repair as necessary. After repairs, go to step  30.
  15. Disconnect injector test light. Using a standard test light connected to ground, probe ignition feed of injector harness connector for each affected/misfiring injector. See SYSTEM WIRING DIAGRAMS article. Crank engine. If test light illuminates, go to step  17. If test light does not illuminate, go to step  19.
  16. Replace any faulty fuel injector(s). After replacing injector(s), go to step  30.
  17. Check affected fuel injector driver circuit(s) for an open, short to ground or short to voltage. See SYSTEM WIRING DIAGRAMS article. If problem is found, go to next step. If circuit is okay, go to step  26.
  18. Repair injector driver circuit(s) as necessary. After repairs, go to step  30.
  19. Repair open ignition feed circuit (Gray wire) between fuel injector harness connector and fuel injector. After repairs, go to step  31.
  20. Remove boot assemblies from affected spark plug cable. Using a DVOM, Check resistance of spark plug cable that did not have a spark. If resistance is less than 30 k/ohms, go to next step. If resistance is not less than 30 k/ohms, go to step  29.
  21. Turn ignition off. Disconnect PCM harness connectors. Reconnect spark test to wire not indicating spark. Turn ignition on. Using fused jumper wire connected to battery voltage, momentarily touch affected Ignition Control (IC) circuit at PCM harness connector. See SYSTEM WIRING DIAGRAMS article. If spark does not exist when jumper wire is removed from IC circuit, go to next step. If spark exists when jumper wire is removed from IC circuit, go to step  26.
  22. Turn ignition off. Disconnect 6-pin Ignition Control Module (ICM) harness connector. Check affected IC circuit identified in step 21)  for open or short. Repair circuit as necessary and go to step  30. If no short or open was found, go to next step.
  23. Remove ignition coil from cylinder that did not spark. Using DVOM, measure secondary coil resistance. If resistance is 5000-8000 ohms, go to next step. If resistance is not 5000-8000 ohms, go to step  29.
  24. Install a known-good ignition coil. Reconnect ICM harness connector. Connect spark tester connected to problem cylinder. Touch affected IC circuit as described in step  21. If spark exists, go to step  30. If spark does not exist, go to next step.
  25. Check ICM harness connections. Repair if necessary. If connections are okay, replace ICM. After replacing module, go to step  30.
  26. Inspect PCM harness connectors. If connectors are okay, go to step  30. If connectors are not okay, go to next step.
  27. Replace PCM. Program replacement PCM using appropriate equipment. See PROGRAMMING . After replacing PCM, go to step  30.
  28. Replace spark plug cables. After replacing cables, go to step  30.
  29. Replace faulty ignition coil. After replacing repairs, go to next step.
  30. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Start engine and allow it to idle. Ensure engine is at normal operating temperature. Operate vehicle within conditions required for setting this DTC. Select SPECIFIC DTC function, then enter DTC P0300. If scan tool indicates TEST RAN AND PASSED, go to next step. If scan tool does not indicate TEST RAN AND PASSED, repeat step  2.
  31. If any other DTCs are set, diagnose DTCs as necessary. If no other DTCs are set, no problem is indicated at this time.
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