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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. Turn ignition on. Verify Malfunction Indicator Light (MIL) is illuminated. If MIL is illuminated, leave ignition on and go to next step. If MIL is not illuminated, go to NO MALFUNCTION INDICATOR LIGHT (CHECK ENGINE LIGHT)  under MALFUNCTION INDICATOR LIGHTS.
  2. Verify Reduced Power Lamp (RPL) is illuminated. If RPL is illuminated, go to next step. If RPL is not illuminated, go to NO REDUCED POWER LAMP  under MALFUNCTION INDICATOR LIGHTS.
  3. Turn ignition off. Connect TECH 2 or equivalent scan tool to DLC. DLC is located under cover on leftside of instrument panel. Follow manufacturer`s instructions for scan tool operation. Turn ignition on. Attempt to display PCM engine data. If scan tool displays PCM engine data, go to next step. If scan tool does not display PCM data, verify scan tool is properly installed. If scan tool is properly installed, go to step  12.
  4. Using scan tool, from MISCELLANEOUS TESTS function, command MIL (CHECK ENGINE lamp) OFF. If MIL turns off, go to next step. If MIL does not turn off, go to MALFUNCTION INDICATOR LIGHT ON STEADY  under MALFUNCTION INDICATOR LIGHTS.
  5. Using scan tool, from MISCELLANEOUS TESTS function, command RPL indicator OFF. If RPL indicator turns off, go to next step. If RPL indicator does not turn off, go to REDUCED POWER LAMP ON STEADY  under MALFUNCTION INDICATOR LIGHTS.
  6. Using scan tool, retrieve and record any stored DTCs. If any DTCs are stored in memory, go to next step. If no DTCs are stored in memory, go to step  11.
  7. If DTCs P0562, P0563, P0601, P0602, P0604, P0606, P1625, P1635, P1639, P1640 or P1650 are stored. Perform appropriate test, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If none of the listed DTCs are stored in memory, go to next step.
  8. If DTCs P1514, P1515, P1516, P1523, P1125, P1290, P1295 or P2299 are stored. Perform appropriate test, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If none of the listed DTCs are stored in memory, go to next step.
  9. If DTCs P0106, P0107, P0336, P0337, P0401, P0405, P0425, P1107, P1120, P1220, P1221, P1271, P1272, P1273, P1275, P1280, P1285, P1404, P1515, P1516, P1635 or P1639 are stored. Perform appropriate test, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If two or more of the listed DTCs are stored, go to MULTIPLE POWERTRAIN CONTROL MODULE INFORMATION SENSOR DIAGNOSTIC TROUBLE CODES SET . If two or more of the listed DTCs are not stored, go to next step.
  10. Attempt to start engine. If starter motor cranks, go to next step. If starter motor does not crank, repair as necessary. See STARTERS article in STARTING & CHARGING SYSTEMS.
  11. Start engine. If engine starts and continues to run, go back to step  6. If engine will not run, go to ENGINE CRANKS BUT WILL NOT RUN under NO START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES article.
  12. Compare PCM data values displayed to typical engine scan data values. If values displayed are normal or close to typical values, OBD-II system check is complete. If driveability problem is still present, go to TROUBLE SHOOTING - NO CODES article. If values are not correct, repair by symptom. See SYSTEM & COMPONENT TESTING article.
  13. Turn ignition off. Disconnect PCM Blue 80-pin harness connectors E-21 and E-22. PCM is located at right rear of engine compartment. Turn ignition on. Check for open, short to ground or short to voltage in class 2 data circuit between DLC terminal No. 2 and PCM harness connector E-21 terminal No. 58 (Orange/Blue wire). See WIRING DIAGRAMS article. Also check for open or short to ground in ignition feed circuit between DLC terminal No. 16 and dash fuse box (Green/White wire). Check for open in DLC ground circuit and DLC terminal No. 4 (Black wire). If problem with wiring is found, repair as necessary. After repairs, repeat testing starting in step  2. If no problems were found, go to next step.
  14. Attempt to reprogram EEPROM. See EEPROM PROGRAMMING PROCEDURE  under POWERTRAIN CONTROL MODULE. Programming PCM/EEPROM requires the use of a scan tool and special manufacturer equipment. After programming attempt to display PCM engine data on scan tool. If data is now displayed, repeat testing starting in step  2. If PCM engine data is not displayed, go to next step.
  15. Replace and reprogram PCM. See POWERTRAIN CONTROL MODULE REPLACEMENT  under POWERTRAIN CONTROL MODULE. Use scan to verify system operation and repeat testing starting in step  2.
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