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Home >> Isuzu >> 1996 >> Hombre XS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Testing >> Trouble Shooting >> Engine Cranks But Will Not Run >> Ignition System
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Ignition System

  1. Perform On-Board Diagnostic (OBD) System Check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  . After performing OBD system check, go to next step.
  2. Check for faulty PCM ground connections at engine block. After repairs, go to step 22). If connections are okay, go to next step.
  3. Check for blown fuse No. 9 (20-amp) or No. 10 (20-amp) located in instrument panel fuse block. If fuses are okay, go to next step. If fuses are faulty, replace as necessary, and go to step 31).
  4. Install scan tool. Turn ignition on. Ensure throttle is closed. Read Throttle Position (TP) sensor value. If TP value is less than one volt, go to next step. If TP sensor value is greater than one volt, diagnose using DTC P0121. See appropriate TESTS W/CODES article.
  5. Check Engine Coolant Temperature (ECT) sensor and Intake Air Temperature (IAT) sensor values. ECT and IAT sensor values should be close to each other. If values are same or similar to each other, go to next step. If value readings vary, diagnose using DTC P0118. See appropriate TESTS W/CODES article.
  6. Check Manifold Absolute Pressure (MAP) sensor voltage while cranking engine. If MAP sensor voltage changes, go to step 9). If MAP sensor voltage does not change, check MAP sensor. See SYSTEM/COMPONENT TESTS article.
  7. Turn ignition off. Disconnect all fuel injector harness connectors. Install fuel injector test (noid) light on any cylinder. Crank engine while observing noid light. Repeat on all injector harness connectors. If noid light flashes on and off on all cylinders, go to next step. If noid light does not flash at all cylinders, go to step 19).
  8. Install fuel pressure gauge. Turn ignition on (it may be necessary to cycle ignition on and off several times to achieve maximum pressure reading). Fuel pressure should be 41-47 psi (2.9-3.3 kg/cm2 ). If fuel pressure is as specified, check TP sensor for open, short, or binding or sticking in WOT position. Also check for water in fuel, fuel contamination and low engine compression. Repair as necessary. If fuel pressure is not as specified, see FUEL SYSTEM DIAGNOSIS.
  9. Using scan tool, read Crankshaft Position (CKP) sensor value while cranking engine. If CKP sensor value changes (0-255 counts), go to next step. If CKP sensor value does not change, go to step 11).
  10. Install Spark Tester (ST-125) on cylinder No. 1. Crank engine while observing spark tester. Repeat for all cylinders. If spark exists at all cylinders, go to step 7). If spark does not exist at all cylinders, go to step 14).
  11. Turn ignition off. Disconnect CKP sensor electrical connector. Turn ignition on. Using a test light connected to ground, probe CKP sensor harness connector terminal "C" (Red wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 32).
  12. Turn ignition off. Using a test light connected to battery voltage, probe CKP sensor harness connector "B" (Pink/Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 20).
  13. Turn ignition on. Connect test light to CKP harness connector terminal "A" (Yellow wire). While viewing scan tool, alternately touch positive and negative terminals of battery. If CKP sensor value changes, go to step 23). If CKP value does not change, go to step 25).
  14. Turn ignition off. Disconnect Ignition Control Module (ICM) 2-pin connector. Connect DVOM between ground and ICM 6-pin connector terminal "D" (Red/Black wire). Check frequency while cranking engine. Repeat procedure with ICM 6-pin connector terminal "E" (Purple/White wire). Both frequency readings should be between 1-10 Hz. If readings are as specified, go to next step. If readings are not as specified, go to step 16).
  15. Turn ignition on. Disconnect 6-pin ICM harness connector. Using DVOM, check voltage between ICM harness 2-pin connector terminals "A" (Black wire) and "B" (Pink wire). If battery voltage is present, go to step 26). If battery voltage is not present, go to step 28).
  16. Turn ignition off. Using a test light connected to battery voltage, probe ICM 6-pin harness connector terminals "D" (Red/Black wire) and "E" (Purple/White wire). If test light illuminates at both terminals, go to step 17). If test light does not illuminate at both terminals, go to step 18).
  17. Disconnect PCM connector C3. Using a test light connected to battery voltage, probe ICM 6-pin harness connector at terminals "D" (Red/Black wire) and "E" (Purple/White wire). If test light illuminates at both terminals, go to step 29). If test light does not illuminate at both terminals, go to step 24).
  18. Turn ignition off. Using DVOM, check resistance between ICM 6-pin connector terminals "D" (Red/Black wire) and "E" (Purple/White wire). Resistance should be infinite. If resistance is as specified, go to step 30). If resistance is not as specified, go to step 29).
  19. If noid light failed to flash on all 4 injectors, check for an open ignition feed circuit (Pink wire). Repair as necessary. After repairs, go to step 33). If circuit is okay, go to step 21).
  20. Check for open CKP sensor ground circuit (Pink/Black wire). Repair as necessary. After repairs, go to step 33). If circuit is okay, go to step 24).
  21. Check for open or grounded circuit in cylinder that did not illuminate injector noid light. After repairs, go to step 33). If circuit is okay, go to step 24).
  22. Repair PCM ground connection. After repairs, go to step 33).
  23. Check CKP sensor harness connector. If harness connector is okay, replace CKP sensor. After repairs, go to step 33).
  24. Check PCM connector C3. If connector is okay, replace PCM. After repairs, go to step 33).
  25. Check for open or short in CKP sensor feed circuit (Yellow wire). Repair as necessary. After repairs, go to step 33). If circuit is okay, go to step 24).
  26. Replace ignition coil for affected cylinder that did not fire. Attempt to start engine. If engine starts, go to step 33). If engine does not start, go to next step.
  27. Replace ICM. After repairs, go to step 33).
  28. Check for open in ground circuit (Black wire) or ignition circuit (Pink wire) to ICM 2-pin connector. Repair as necessary. After repairs, go to step 33).
  29. Check for short in ignition control circuit "A" to PCM connector C3 terminal No. 32 (Purple/White wire). Check for short in ignition control circuit "B" to PCM connector C3 terminal No. 31 (Red/Black wire). Repair as necessary. After repairs, go to step 33). If circuits are okay, go to step 24).
  30. Check for short or open in ignition control circuit "A" to PCM connector C3 terminal No. 32 (Purple/White wire). Check for short or open in ignition control circuit "B" to PCM connector C3 terminal No. 31 (Red/Black wire). Repair as necessary. After repairs, go to step 33). If circuits are okay, go to step 25).
  31. Check for short to ground in fuel pump circuit (Orange or Gray wire) and injector/ignition feed circuit (Pink wire). See appropriate wiring diagram in WIRING DIAGRAMS  section. Repair as necessary. Replace blown fuse. After repairs, go to step 33).
  32. Check for open or short in Camshaft Position (CMP) sensor feed circuit (Red wire). Repair as necessary. After repairs, go to step 33). If circuit is okay, go to step 25).
  33. Clear DTC(s) using scan tool. After clearing DTC(s), attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start or starts and dies/stalls, go to step 2).
  34. Warm engine to normal operating temperature. Check if any DTCs are set. If any DTCs are present, diagnose DTC(s). See appropriate TESTS W/CODES article.
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