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Home >> Chevrolet >> 2003 >> Avalanche 2500, RWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Diagnostic Procedures - 8.1L >> Ignition Systems >> Electronic Ignition System >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article. After performing diagnostic system check, go to next step.
  2. Crank engine. Observe engine speed parameter with a scan tool. Does scan tool display engine RPM? If yes, go to next step. If no, go to step  16 .
  3. Is DTC P0335, P0336 or P0351-P0358 also set? If yes, diagnose affected DTC(s). See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article. If DTC P0335, P0336 or P0351-P0358 are not set, go to next step.
  4. Attempt to start engine. Does engine start and run? If yes, go to next step. If no, go to step  9 .
  5. Idle engine. Observe misfire current counters on scan tool. Does scan tool display any misfire current counters incrementing? If yes, go to next step. If no, go to DIAGNOSTIC AIDS  .
  6. Do misfire current counters increment for most cylinders on one bank of engine? If yes, go to step  12 . If no, go to next step.
  7. 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 spark plug using Spark Tester (J-26792) while cranking. A few sparks, then nothing is considered no spark. Is adequate spark present? If yes, go to step  33 . If no, go to next step.
  8. Measure spark plug wire resistance. Is resistance more than 1000 ohms per foot? If yes, go to step  32 . If no, go to next step.
  9. Turn ignition off. Disconnect ignition coil that corresponds to Misfire Current counter that was incrementing. Turn ignition on, with engine off. Probe ignition 1 voltage circuit of ignition coil with a test light connected to a good ground. See Figure or Figure . Does test light illuminate? If yes, go to next step. If no, go to step  13 .
  10. Probe ignition 1 voltage circuit at ignition coil with a test light connected to ground circuit of ignition coil. Does test light illuminate? If yes, go to next step. If no, go to step  14 .
  11. Probe ignition 1 voltage circuit at ignition coil with a test light connected to low reference circuit of ignition coil. Does test light illuminate? If yes, go to step  20 . If no, go to step  15 .
  12. Inspect for an open INJ "A" or INJ "B" fuse. Is fuse open? If yes, go to step  29 . If no, go to step  23 .
  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 step  24 . If no, go to step  23 .
  14. Disconnect main ignition coil 8-way connector. Probe ignition 1 voltage circuit on harness side with a test light connected to ground circuit of ignition coil. Does test light illuminate? If yes, go to step  18 . If no, go to step  26 .
  15. Disconnect main ignition coil 8-way connector. Probe ignition 1 voltage circuit on harness side with a test light connected to low reference circuit of ignition coil. Does test light illuminate? If yes, go to step  19 . If no, go to step  28 .
  16. Turn ignition on, with engine off. Disconnect CKP sensor. See Figure . Measure voltage from CKP sensor 12-volt reference circuit and a good ground with DVOM. See Figure . Compare measured voltage with system voltage. Is difference in voltage more than 0.5 volt? If yes, go to next step. If no, go to step  30 .
  17. Test for a short to ground in CKP 12-volt reference circuit or CMP sensor 12-volt reference circuit. See Figure , Figure or Figure . Did you find and correct condition? If yes, go to step  35 . If no, go to step  22 .
  18. Test for an intermittent and for a poor connection at ignition coil 8-way connector. Did you find and correct condition? If yes, go to step  35 . If no, go to step  25 .
  19. Test for an intermittent and for a poor connection at ignition coil 8-way connector. Did you find and correct condition? If yes, go to step  35 . If no, go to step  27 .
  20. Test for an intermittent and for a poor connection at ignition coil. Did you find and correct condition? If yes, go to step  35 . If no, go to step  31 .
  21. Test for an intermittent and for a poor connection at CKP sensor. Did you find and correct condition? If yes, go to step  35 . If no, go to step  30 .
  22. Test for an intermittent and for a poor connection at PCM. Did you find and correct condition? If yes, go to step  35 . If no, go to step  34 .
  23. Repair open or high resistance in ignition 1 voltage circuit between fuse block and splice. After repairs, go to step  35 .
  24. Repair open or high resistance in ignition 1 voltage circuit between splice and ignition coil connector. After repairs, go to step  35 .
  25. Repair open in ground circuit between main 8-way connector and ignition coil. After repairs, go to step  35 .
  26. Repair open in ground circuit. After repairs, go to step  35 .
  27. Repair open in low reference circuit between main 8-way connector and ignition coil. After repairs, go to step  35 .
  28. Repair open in low reference circuit between PCM and splice. After repairs, go to step  35 .
  29. Repair ignition 1 voltage for a short to ground. Replace fuse. After repairs, go to step  35 .
  30. Replace CKP sensor. After replacing sensor, go to step  35 .
  31. Replace ignition coil. After replacing ignition coil, go to step  35 .
  32. Replace spark plug wire. After replacing spark plug wire, go to step  35 .
  33. Replace spark plug. After replacing spark plug, go to step  35 .
  34. Replace PCM. See appropriate REMOVAL & INSTALLATION article. After replacing PCM, go to next step.
  35. Attempt to start engine. Does engine start and continue to run? If yes, go to next step. If no, go to step  2 .
  36. Clear DTCs with a scan tool. Turn ignition off for 30 seconds. Start engine. Let engine reach operating temperature. Are there any DTCs that have not been diagnosed? If yes, diagnose affected DTC(s). See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article. If no DTC(s) are set, system is okay.
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