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Diagnostic Procedures

WARNING: This page is about a different car, the 2003 GMC Sonoma and 2003 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 2.2L SONOMA & S10 PICKUP article. After performing diagnostic system check, go to next step.
  2. Attempt to start engine. Does engine start and run? If yes, go to step  5 . If no, go to next step.
  3. Is the ECM 1 fuse open (located in underhood fuse/relay block)? If yes, go to step  23 . If no, go to next step.
  4. Crank engine. Observe the CKP Active Counter parameter on scan tool. Does the CKP Active Counter parameter increment? If yes, go to next step. If no, go to step  8 .
  5. Remove fuel pump relay (located in underhood fuse/relay block). Install Spark Tester (J-26792) on cylinder No. 1 spark plug wire. Leave the other 3 ignition wires connected to spark plugs. Observe the spark tester while cranking engine. Repeat the procedure on cylinders No. 2, 3 and 4. Does spark occur on all cylinders? If yes, go to next step. If no, go to step  13 .
  6. Turn ignition off. Remove and inspect spark plugs. Did you find a condition? If yes, go to step  26 . If no, go to next step.
  7. Inspect for basic engine problems. Did you find and correct the condition? If yes, go to step  31 . If no, go to DIAGNOSTIC AIDS  .
  8. Turn ignition off. Disconnect the IC module 2-pin harness connector, located on module base. Turn ignition on, with engine off. Measure voltage from the ignition 1 voltage circuit of the ICM to the ground circuit of the ICM at the harness connector with a DVOM. If battery voltage is present, go to step  10 . If battery voltage is not present, go to next step.
  9. Measure the voltage from the ignition 1 voltage circuit of the IC and a good ground with a DVOM. If battery voltage is present, go to step  24 . If battery voltage is not present, go to step  25 .
  10. Disconnect the IC module 6-pin harness connector, located on module base. Measure the resistance from the CKP sensor 1 signal circuit and the low reference circuit at the harness connector with a DVOM. Does the resistance measure within 700-1350 ohms? If yes, go to next step. If no, go to step  17 .
  11. Crank engine. Measure the frequency between the CKP sensor 1 signal circuit and the low reference circuit with a DVOM. Does the frequency measure within 28-32 Hz? If yes, go to next step. If no, go to step  27 .
  12. Observe the CKP activity counter parameter on scan tool. Momentarily touch a test light to the low resolution engine speed signal circuit connected to battery voltage. Does the CKP Activity Counter increment? If yes, go to step  21 . If no, go to step  19 .
  13. Disconnect the 6-pin ICM harness connector. Measure the AC voltage from the IC timing control circuit of the ICM and a good ground with a DVOM. Crank engine. Is voltage within 1-3 volts? If yes, go to next step. If no, go to step  15 .
  14. Measure the AC voltage from the IC timing control "B" circuit of the ICM and a good ground with a DVOM. Crank engine. Is voltage within 1-3 volts? If yes, go to step  20 . If no, go to step  16 .
  15. Test the IC timing control circuit for an open, short to ground, short to voltage, or short to IC timing control "B". Did you find and correct the condition? If yes, go to step  31 . If no, go to step  22 .
  16. Test the IC timing control circuit "B" for an open, short to ground, or short to voltage. Did you find and correct the condition? If yes, go to step  31 . If no, go to step  22 .
  17. Test the CKP sensor 1 signal circuit for a faulty connection, open, short to ground, or short to voltage. Did you find and correct the condition? If yes, go to step  31 . If no, go to next step.
  18. Test the CKP sensor low reference circuit for a faulty connection, open circuit, short to ground or short to voltage. Did you find and correct the condition? If yes, go to step  31 . If no, go to step  27 .
  19. Test the low resolution engine speed circuit for a faulty connection, open, short to ground, or short to voltage. Did you find and correct the condition? If yes, go to step  31 . If no, go to step  22 .
  20. Connect the ICM 6-pin harness connector. Exchange the ignition coil positions. Using the procedure in step  5 , recheck for spark. Does the no-spark condition move with the coil? If yes, go to step  28 . If no, go to next step.
  21. Test for intermittent and poor connection at the ICM. Did you find and correct the conditions? If yes, go to step  31 . If no, go to step  29 .
  22. Test for intermittent and poor connection at the PCM. Did you find and correct the conditions? If yes, go to step  31 . If no, go to step 30.
  23. Repair short to ground in the ignition 1 voltage circuit. Replace the fuse. After repairs, go to step  31 .
  24. Repair open in the ICM ground circuit. After repairs, go to step  31 .
  25. Repair open in the ignition 1 voltage circuit. After repairs, go to step  31 .
  26. Replace spark plugs. After replacing spark plus, go to step  31 .
  27. Replace CKP sensor. After replacing sensor, go to step  31 .
  28. Replace the affected coil. After replacing affected coil, go to step  31 .
  29. Replace ICM. After replacing ICM, go to step  31 .
  30. Replace PCM. See REMOVAL & INSTALLATION - BLAZER, SONOMA & S10 PICKUP article. After replacing PCM, go to next step.
  31. Turn ignition off for 30 seconds. Start engine and operate vehicle. Observe the MIL, vehicle performance and driveability. Does the vehicle operate normally, with no MIL illumination and no stored DTCs? If yes, system is okay. If no, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 2.2L SONOMA & S10 PICKUP article.
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