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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Controls - System & Component Testing >> Ignition System >> Electronic Ignition System Diagnosis (4.8L, 5.3L, 6.0L & 8.1L) >> Diagnostic Procedure

Diagnostic Procedure

  1. Perform Diagnostic System Check - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing Diagnostic System Check - Engine Controls, go to next step.
  2. Crank the engine. Use a scan tool in order to observe engine speed parameter. Does scan tool display engine RPM? If yes, go to next step. If no, go to step  25.
  3. Are DTCs P0335, P0336, or P0351-P0358 set? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article. If no, go to next step.
  4. Install scan tool. Idle engine. Use a scan tool in order to monitor all Misfire Current counters on misfire data list. Do any of Misfire Current counters increment? If yes, go to next step. If no, go to DIAGNOSTIC AIDS .
  5. Do misfire current counters increment for most cylinders on one bank of engine? If yes, go to step  11. If no, go to next step.
    6. NOTE: A few sparks, then nothing, is considered no spark.
  6. Inspect spark plug wire for open circuits, cracks, or improper seating of terminals at spark plug or coil before proceeding with test. Inspect for spark at plug with Spark Tester (J 26792) while cranking. Is adequate spark present? If yes, go to step  31. If no, go to next step.
  7. Measure spark plug wire resistance. Does resistance measure near 460-720 ohms/ft? If yes, go to next step. If no, go to step  30.
  8. Turn OFF the ignition. Disconnect ignition coil electrical harness connector that corresponds to Misfire Current counter that was incrementing. Turn ON the ignition, with the engine OFF. Probe Ignition 1 voltage circuit at ignition coil electrical connector with test light connected to battery ground. Does test light illuminate? If yes, go to next step. If no, go to step  13.
  9. Probe Ignition 1 voltage circuit at ignition coil electrical connector to ignition coil ground circuit with test light. Does test light illuminate? If yes, go to next step. If no, go to step  16.
  10. Probe Ignition 1 voltage circuit at ignition coil electrical connector to ignition coil low reference circuit with test light. Does test light illuminate? If yes, go to step  24. If no, go to step  20.
  11. Inspect for an open ignition coil fuse. Locate and repair Ignition 1 voltage circuit for a grounded circuit if fuse is open. Replace fuse. Did you find and correct the condition? If yes, go to step  34. If no, go to next step.
  12. Repair open in Ignition 1 voltage circuit between fuse block and splice. After repairs, go to step  34.
  13. Disconnect main ignition coil 8-way connector. Probe Ignition 1 voltage circuit at ignition coil main 8-way connector using test light connected to battery ground. Does test light illuminate? If yes, go to next step. If no, go to step  15.
  14. Repair open Ignition 1 voltage circuit between splice and ignition coil connector. After repairs, go to step  34.
  15. Repair open Ignition 1 voltage circuit between fuse block fuse and splice. After repairs, go to step  34.
  16. Disconnect main ignition coil 8-way connector. Probe coil Ignition 1 voltage circuit to ignition coil ground circuit at ignition coil main electrical 8-way connector using test light connected to battery ground. Does test light illuminate? If yes, go to next step. If no, go to step  19.
  17. Inspect for a poor connection at main ignition coil 8-way electrical connector. Repair poor connections as necessary. Did you find and correct the condition? If yes, go to step  34. If no, go to next step.
  18. Repair open ground circuit between main 8-way connector and ignition coil connector. After repairs, go to step  34.
  19. Repair open ground circuit between ground and main 8-way connector. After repairs, go to step  34.
  20. Disconnect main ignition coil 8-way connector. Probe Ignition 1 voltage circuit at ignition coil main electrical 8-way connector to ignition coil low reference circuit using test light. Does test light illuminate? If yes, go to next step. If no, go to step  23.
  21. Inspect for a poor connection at main ignition coil electrical 8-way connector. If a poor connection is found, repair as necessary. Did you find and correct the condition? If yes, go to step  34. If no, go to next step.
  22. Repair open low reference circuit between main 8-way connector and ignition coil connector. After repairs, go to step  34.
  23. Repair open low reference circuit between PCM and splice. After repairs, go to step  34.
  24. Inspect for poor connections at ignition coil harness connector. Repair poor connections as necessary. Did you find and correct the condition? If yes, go to step  34. If no, go to step  29.
  25. Turn ON the ignition, with the engine OFF. Disconnect CKP sensor harness connector. Measure voltage from CKP sensor 12-volt reference circuit and a good ground using DMM. Is voltage near battery voltage? If yes, go to next step. If no, go to step  28.
  26. Inspect for poor connections at CKP sensor. Did you find and correct the condition? If yes, go to step  34. If no, go to next step.
  27. Replace CKP sensor. After repairs, go to step  34.
  28. Test for a short to ground in CKP sensor 12-volt reference circuit and CMP sensor 12-volt reference circuit. Did you find and correct the condition? If yes, go to step  34. If no, go to step  32.
  29. Replace ignition coil. After repairs, go to step  34.
  30. Replace spark plug wire. After repairs, go to step  34.
  31. Replace spark plug. After repairs, go to step  34.
  32. Inspect for poor connections at PCM. Did you find and correct the condition? If yes, go to step  34. If no, go to next step.
  33. Replace PCM. Program replacement PCM. See POWERTRAIN CONTROL MODULE under PROGRAMMING in appropriate SELF-DIAGNOSTICS article. After repairs, go to step  34.
  34. Attempt to start engine. Does engine start and continue to run? If yes, go to next step. If no, go to step  2.
  35. Turn OFF engine for 30 seconds. Start engine and operate vehicle. Observe MIL, vehicle performance, and driveability. Does vehicle operate normally, with no MIL illumination and no stored DTCs? If yes, system is okay. If no, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.
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