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Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Pontiac Grand Prix, 2003 Chevrolet Malibu, and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: The ignition relay diagnostic procedure assumes that the vehicle battery is fully charged.
  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. After performing diagnostic system check - engine controls, go to next step.
  2. Turn ignition switch to RUN position, engine OFF. Remove the underhood junction block cover. Probe the following fuses using a test light connected to a good ground:

    Century

    • OXY SEN
    • ELEK IGN
    • F/INJR
    • TRANS
    • ENG EMIS

    Grand Prix

    • INJ
    • IGN 1 UH
    • ELEK IGN
    • TCC
    • A/C CLU/ABS IGN

    Does the test light illuminate on at least one test point of each fuse? If yes, go to next step. If no, go to step  11.

  3. Turn ignition switch to OFF position. Probe both test points of the A/C ENG EMIS (Century) or CLU/ABS IGN (Grand Prix) fuse using a test light connected to a good ground. Does the test light illuminate on either test point of the fuse? If yes, go to next step. If no, go to step  36.
  4. Turn ignition switch to OFF position. Remove the ignition relay from the underhood junction block using Relay Puller Pliers (J 43244). See Fig 1. Probe both test points of the PCM-BCM fuse (Century) or ECM fuse (10-amp) in the Instrument Panel (IP) fuse block using a test light connected to a good ground. See WIRING DIAGRAMS . Does the test light illuminate on any of the fuse test points? If yes, go to step  8. If no, go to next step.
  5. Test the ignition relay load circuit bus bar of the underhood junction block between the ignition relay and the fuses to the circuit components for a short to battery positive voltage. Did you find a condition? If yes, go to step  35. If no, go to next step.
  6. Remove the following fuses from the underhood junction block. See WIRING DIAGRAMS .

    Century

    • OXY SEN
    • ELEK IGN
    • F/INJR
    • TRANS
    • ENG EMIS

    Grand Prix

    • INJ
    • IGN 1 UH
    • ELEK IGN
    • TCC
    • A/C CLU/ABS IGN

    Probe all these fuse terminals in the underhood junction block using a test light connected to a good ground. Does the test light illuminate at any of the fuse terminals? If yes, go to next step. If no, go to step  32.

  7. Remove the A/C clutch relay from the underhood junction block using the relay puller pliers. Probe both fuse terminals of the ENG EMISS (Century) or A/C CLU/ABS IGN (Grand Prix) fuse in the underhood junction block using a test light connected to a good ground. Does the test light illuminate on either fuse terminal? If yes, diagnose engine electrical system. See ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate GENERATORS & REGULATORS article. If no, go to step  34.
  8. Disconnect the ignition switch harness connector. Connect a 20-amp fused jumper wire from the ignition switch connector battery positive voltage terminal to the corresponding terminal at the vehicle harness connector. Probe the ignition 1 voltage circuit at the ignition switch harness connector with a test light connected to a good ground. Does the test light illuminate? If yes, go to step  30. If no, go to next step.
  9. Remove the following fuses from the I/P fuse block. See WIRING DIAGRAMS .

    Century

    • TURN SIGNALS, CORN LPS
    • AIR BAG
    • CLUSTER
    • PCM, BCM, U/H RELAY

    Grand Prix

    • TURN
    • SIR (Air Bag)
    • IP-IGN
    • CRUISE
    • PCM

    Probe the ignition switch harness connector ignition 1 voltage circuit that leads to the I/P fuse block, using a test light connected to a good ground. Does the test light illuminate? If yes, go to step  30. If no, go to next step.

  10. Disconnect the underhood junction block harness connector that contains the ignition relay ignition 1 voltage circuit. Probe the ignition relay ignition 1 voltage circuit at the underhood junction block vehicle harness connector using a test light connected to a good ground. Does the test light illuminate? If yes, go to step  31. If no, go to step  35.
  11. Turn ignition switch to OFF position. Probe both test points of the 30-amp IGN 1 fuse in the underhood junction block using a test light connected to a good ground. Does the test light illuminate on both test points of the fuse? If yes, go to step  15. If no, go to next step.
  12. Does the test light illuminate on one test point of the 30-amp IGN 1 fuse? If yes, go to next step. If no, go to step  21.
  13. Test the battery positive voltage circuit between the underhood junction block and the ignition switch for a short to ground. Did you find and correct the condition? If yes, go to step  36. If no, go to next step.
  14. Test the ignition 1 voltage circuit between the ignition switch and the 10-amp PCM, BCM, U/H relay (Century) or 10-amp ECM fuse (Grand Prix) terminals in the I/P fuse block for a short to ground. Did you find and correct the condition? If yes, go to step  36. If no, go to step  33.
  15. Turn ignition switch to RUN position, engine OFF. Probe both test points of the 10-amp ECM fuse using a test light connected to a good ground. Does the test light illuminate on both test point of the fuse? If yes, go to step  22. If no, go to next step.
  16. Does the test light illuminate on one test point of the 10-amp PCM, BCM, U/H relay (Century) 10-amp ECM fuse (Grand Prix)? If yes, go to step  19. If no, go to next step.
  17. Test the ignition 1 voltage circuit between the ignition switch and the PCM, BCM, U/H relay (Century) 10-amp ECM fuse (Grand Prix) for a high resistance or for an open. Did you find and correct the condition? If yes, go to step  36. If no, go to next step.
  18. Test the battery positive voltage circuit between the underhood junction block and the ignition switch for a high resistance or for an open. Did you find and correct the condition? If yes, go to step  36. If no, go to step  33.
  19. Test the ignition 1 voltage circuit between the I/P fuse block and the underhood junction block for a short to ground. Did you find and correct the condition? If yes, go to step  36. If no, go to next step.
  20. Test the underhood junction block, ignition 1 voltage bus bar circuit to the ignition relay for a short to ground. Did you find a condition? If yes, go to step  35. If no, go to step  32.
  21. Turn ignition switch to OFF position. Probe the mounting stud for the battery positive cable at the underhood junction block using a test light connected to a good ground. Does the test light illuminate? If yes, go to step  35. If no, diagnose engine electrical system. See ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate GENERATORS & REGULATORS article.
  22. Turn ignition switch to OFF position. Remove the ignition relay using the relay puller pliers, from the underhood junction block. Probe the ignition relay battery positive voltage circuit at the underhood junction block using a test light connected to a good ground. Does the test light illuminate? If yes, go to next step. If no, go to step  35.
  23. Turn ignition switch to RUN position, engine OFF. Probe the ignition relay ignition 1 voltage circuit at the underhood junction block using a test light connected to a good ground. Does the test light illuminate? If yes, go to step  25. If no, go to next step.
  24. Test the ignition 1 voltage circuit between the I/P fuse block and the underhood junction block for a high resistance or for an open. Did you find and correct the condition? If yes, go to step  36. If no, go to step  35.
  25. Turn ignition switch to RUN position, engine OFF. Probe the ignition relay coil ground circuit at the underhood junction block using a test light connected to battery voltage. Does the test light illuminate? If yes, go to step  27. If no, go to next step.
  26. Turn ignition switch to OFF position. Disconnect the negative battery cable at the battery. Disconnect the underhood junction block harness connector that contains the relay coil ground circuit. Test the ignition relay coil ground circuit at the underhood junction block harness connector for a high resistance or for an open. Did you find and correct the condition? If yes, go to step  36. If no, go to step  35.
  27. Turn ignition switch to OFF position. Jumper the ignition relay battery positive voltage circuit and the ignition relay load circuit together at the underhood junction block using a 20-amp fused jumper wire. Probe the following fuses using a test light connected to a good ground. See WIRING DIAGRAMS .

    Century

    • OXY SEN
    • ELEK IGN
    • F/INJR
    • TRANS
    • ENG EMIS

    Grand Prix

    • INJ
    • IGN 1 UH
    • ELEK IGN
    • TCC
    • A/C CLU/ABS IGN

    Does the test light illuminate on at least one test point of each fuse? If yes, go to next step. If no, go to step  35.

  28. Remove the A/C clutch relay from the underhood junction block using the relay puller pliers. Probe the A/C clutch relay ignition 1 voltage circuit using a test light connected to a good ground. Does the test light illuminate? If yes, go to next step. If no, go to step  35.
  29. Test for an intermittent and for a poor connection at the underhood junction block, ignition relay connector location. Did you find a condition? If yes, go to step  35. If no, go to step  32.
  30. Repair the short to battery positive voltage in the ignition 1 voltage circuit between the ignition switch and the I/P fuse block. After repair, go to step  36.
  31. Repair the short to battery positive voltage in the ignition 1 voltage circuit between the I/P fuse block and the underhood junction block harness connector. After repair, go to step  36.
  32. Replace the ignition relay. After repair, go to step  36.
  33. Replace the ignition switch. After repair, go to step  36.
  34. Replace the A/C clutch relay. After repair, go to step  36.
  35. Replace the underhood junction block. After repair, go to next step.
  36. Replace any open fuses. Turn ignition switch to OFF position for 30 seconds. Attempt to start the engine. Does the engine start and run? If yes, go to next step. If no, diagnose no start condition. Go to NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 3.1L CENTURY, GRAND PRIX & MALIBU article.
  37. Clear the DTCs using a scan tool. Operate the vehicle for 5 minutes. Does a DTC set during this ignition cycle? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 3.1L CENTURY, GRAND PRIX & MALIBU article. If no, system is okay at this time.
Fig 1: Removing Relay Using Relay Puller Pliers
G00227013Courtesy of GENERAL MOTORS CORP.
Fig 2: Identifying Instrument Panel Fuse Block (Century & Grand Prix)
G00227014Courtesy of GENERAL MOTORS CORP.
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