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Home >> Buick >> 2003 >> Century Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System Testing & Engine Component Tests - 3.1L >> Ignition Systems >> Electronic Ignition System Diagnosis >> Diagnostic Procedure
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Diagnostic Procedure

  1. Perform Diagnostic System Check - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.1L CENTURY, GRAND PRIX & MALIBU article.
  2. Attempt to start the engine. Does the engine start and run? If yes, go to next step. If no, go to step  4.
  3. Disconnect the CKP sensor "B" harness connector from the Ignition Control Module (ICM). Measure the resistance from the CKP sensor 1 signal circuit to the low reference circuit of CKP sensor "B" using a DVOM. Is the resistance 800-1200 ohms? If yes, go to next step. If no, go to step  28.
  4. Disconnect the CKP sensor "A" harness connector located on the front of the engine near A/C compressor. Observe the 3X crank sensor parameter using a scan tool. Crank the engine. Does the scan tool indicate a 3X crank sensor signal is present? If yes, go to next step. If no, go to step  11.
  5. Connect CKP sensor "A". Check for spark at each cylinder using Spark Tester (J 26792), or equivalent. Did you observe any non-sparking cylinders? If yes, go to next step. If no, go to step  9.
    6. NOTE: An arching spark plug wire or an arching ignition coil to the ICM may cause a stall or a no start condition.
  6. Check and test the affected cylinder spark plug wires, the ignition coils, and the spark plugs for a short to ground or an arching to ground. If carbon tracking or corrosion is present, replace both components that are affected. Did you find and correct the condition? If yes, go to step  32. If no, go to next step.
  7. Test the resistance of the spark plug wires. Is the resistance more than 3000 ohms per foot? If yes, go to step  30. If no, go to next step.
  8. Measure the ignition coils secondary resistance. Is the resistance 5-8 k/ohms? If yes, go to step  25. If no, go to next step.
  9. Check the spark plug wires for proper routing and for the correct firing order. If any spark plug wires are found to be misrouted, reroute as necessary. Did you find and correct the condition? If yes, go to step  32. If no, go to next step.
  10. Remove and inspect the spark plugs. Did you find the problem? If yes, go to step  31. If no, go to DIAGNOSTIC AIDS .
  11. Connect the CKP sensor "A". Disconnect the ICM harness connector. Turn ignition switch to RUN position. Connect a test light between the ICM ignition 1 voltage circuit and a good ground. Does the test light illuminate? If yes, go to next step. If no, go to step  24.
  12. Connect a test light between the ICM ignition 1 voltage circuit and the ICM ground circuit. Does the test light illuminate? If yes, go to next step. If no, go to step  26.
  13. Test for an intermittent and for a poor connection at the ICM. Did you find and correct the condition? If yes, go to step  32. If no, go to next step.
  14. Disconnect the CKP sensor "B" connector from the ICM. Probe the CKP sensor 1 signal circuit of the CKP sensor "B" using a test light connected to battery voltage. Does the test light illuminate? If yes, go to step  17. If no, go to next step.
  15. Probe the CKP sensor 1 signal circuit of the CKP sensor "B" using a test light connected to a good ground. Does the test light illuminate? If yes, go to step  18. If no, go to next step.
  16. Turn ignition switch to OFF position. Measure the resistance from the CKP sensor 1 signal circuit and the low reference circuit of the CKP sensor "B" using the DVOM at the ICM harness connector. Is the resistance 800-1200 ohms? If yes, go to step  27. If no, go to step  19.
  17. Test the CKP sensor 1 signal circuit for a short to ground. Did you find and correct the condition? If yes, go to step  32. If no, go to step  20.
  18. Test the CKP sensor 1 signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step  32. If no, go to step  17.
  19. Test the CKP sensor "B" circuits for the following conditions:
    • An open.
    • The CKP sensor 1 signal and the low reference circuit shorted together.

    Did you find and correct the condition? If yes, go to step  32. If no, go to step  17.

  20. Test for an intermittent and for a poor connection at the ICM. Did you find and correct the condition? If yes, go to step  32. If no, go to next step.
  21. Test for an intermittent and for a poor connection at the CKP sensor. Did you find and correct the condition? If yes, go to step  32. If no, go to next step.
  22. Remove the CKP sensor. Visually inspect the CKP sensor for the following conditions:
    • Physical damage.
    • Loose or improper installation.
    • Wiring routed too closely to secondary ignition components.

    Did you find and correct the condition? If yes, go to step  32. If no, go to next step.

  23. Visually inspect the reluctor wheel for the following conditions:
    • Physical damage.
    • Loose or improper installation.

    Did you find and correct the condition? If yes, go to step  32. If no, go to step  28.

  24. Repair the open or the short to ground in the ICM ignition 1 voltage circuit. Replace the fuse if necessary. After repair, go to step  32.
  25. Remove the coils associated with the cylinder that did not have spark. Connect a test light across the ignition module primary circuit, between the ICM terminals for the coils. Observe the test light while cranking the engine. Does the test light flash continuously while the engine is being cranked? If yes, go to step  29. If no, go to step  27.
  26. Repair the open in the ICM ground circuit. After repair, go to step  32.
  27. Replace the ICM. After repair, go to step  32.
  28. Replace the CKP sensor "B". After repair, go to step  32.
  29. Replace the affected ignition coils. After repair, go to step  32.
  30. Replace the spark plug wires. After repair, go to step  32.
  31. Replace the spark plugs. After repair, go to next step.
  32. Turn ignition switch to OFF position for 30 seconds. Start the engine and operate the vehicle. Observe the Malfunction Indicator Light (MIL), vehicle performance and driveability. Does the vehicle operate normal, with no MIL? If yes, system is okay at this time. If no, go to step  2.
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