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Home › Saturn › 2003 › L300 › Repair and Diagnosis › Engine Performance › System › Engine Controls - System & Component Testing › Motors, Relays & Solenoids › Main Relay › Diagnostic Procedure

Diagnostic Procedure

NOTE: The main relay system diagnosis table assumes that the vehicle battery is fully charged.
  1. If diagnostic system check has already been performed, go to next step. If diagnostic system check has not been performed, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.0L SATURN "L" SERIES article.
  2. Turn ignition ON, with engine OFF. Remove underhood fuse block cover. Probe the following fuses with a test light that is connected to a good ground:
    • ENGINE CNTL 1 FUSE
    • ENGINE CNTL 2 FUSE
    • ENGINE CNTL 3 FUSE
    If test light illuminates on at least one test point of each fuse, go to next step. If test light does not illuminate on at least one test point, go to step  11 .
  3. Turn ignition OFF. Probe both test points of the 10-amp ENGINE CNTL 3 fuse in the underhood fuse block with a test light that is connected to a good ground. If test light illuminates on either test point of the fuse, go to step  4 . If test light does not illuminate on either test point, go to step  38 .
  4. Remove main relay from the underhood fuse block. Probe both the test points of the 10-amp ENGINE CNTL 3 fuse with a test light that is connected to a good ground. If the test light illuminates on either test point of the fuse, go to next step. If test light does not illuminate on either test point, go to step  8 .
  5. Remove the ENGINE CNTL 1 fuse from the underhood fuse block. Probe both test points of the 10-amp ENGINE CNTL 3 fuse with a test light that is connected to a good ground. If test light illuminates on either test point of the fuse, go to next step. If test light does not illuminate on either test point, see appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  6. Remove the ENGINE CNTL 2 fuse from the underhood fuse block. Probe both test points of the 10-amp ENGINE CNTL 3 fuse with a test light that is connected to a good ground. If test light illuminates on either test point of the fuse, go to next step. If test light does not illuminate on either test point, see appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  7. Remove the ENGINE CNTL 3 fuse from the underhood fuse block. Probe the main relay load circuit bus bar terminal in the underhood fuse block with a test light that is connected to a good ground. If test light illuminates, go to step  35 . If test light does not illuminate, see appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  8. Probe the main relay coil control circuit terminal in the underhood fuse block with a test light that is connected to battery positive voltage. If test light illuminates, go to next step. If test light does not illuminate, go to step  24 .
  9. Disconnect the Engine Control Module (ECM) electrical connector that contains the relay coil control circuit. Probe the main relay coil control circuit terminal in the underhood fuse block with a test light that is connected to battery positive voltage. If the test light illuminates, go to next step. If test light does not illuminate, go to step  31 .
  10. Disconnect the negative battery cable at the battery. Disconnect the underhood fuse block electrical connector that contains the main relay coil control circuit. Probe the main relay coil control circuit at the underhood fuse block electrical connector with a test light that is connected to battery positive voltage. If the test light illuminates, go to step  32 . If test light does not illuminate, go to step  35 .
  11. Remove the main relay from the underhood fuse block. Probe the battery positive voltage terminal for the relay coil in the underhood fuse block with a test light that is connected to a good ground. If the test light illuminates, go to step  13 . If test light does not illuminate, go to next step.
  12. Probe the mounting stud for the positive battery cable at the underhood fuse block with a test light that is connected to a good ground. If the test light illuminates, go to step  35 . If test light does not illuminate, see appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  13. Probe the relay coil control circuit terminal in the underhood fuse block with a test light that is connected to a good ground. If the test light illuminates, go to step  17 . If test light does not illuminate, go to next step.
  14. Turn ignition ON, with engine OFF. Probe the relay coil control circuit terminal in the underhood fuse block with a test light that is connected to a good ground. If the test light illuminates, go to next step. If test light does not illuminate, go to step  19 .
  15. Turn ignition OFF. Disconnect the ECM electrical connector that contains the relay coil control circuit. Turn ignition ON, with engine OFF. Probe the main relay coil control circuit at the underhood fuse block with a test light that is connected to a good ground. If the test light illuminates, go to next step. If test light does not illuminate, go to step  31 .
  16. Turn ignition OFF. Disconnect the negative battery cable at the battery. Disconnect the underhood fuse block electrical connector that contains the main relay coil control circuit. Disconnect the main relay coil connector circuit terminal from the underhood fuse block electrical connector. Connect the electrical connector that contains the main relay coil control circuit to the underhood fuse block. Connect the negative battery cable at the battery. Turn ignition ON, with engine OFF. Probe the main relay coil control circuit terminal at the underhood fuse block electrical connector with a test light that is connected to a good ground. If the test light illuminates, go to step  33 . If test light does not illuminate, go to step  35 .
  17. Turn ignition OFF. Disconnect the ECM electrical connector that contains the relay coil control circuit. Probe the main relay coil control circuit terminal in the underhood fuse block with a test light that is connected to a good ground. If the test light illuminates, go to next step. If test light does not illuminate, go to step  31 .
  18. Disconnect the negative battery cable at the battery. Disconnect the underhood fuse block electrical connector that contains the main relay coil control circuit. Connect the negative battery cable at the battery. Probe the main relay coil connector circuit at the underhood fuse block electrical connector with a test light that is connected to a good ground. If the test light illuminates, go to step  33 . If test light does not illuminate, go to step  35 .
  19. Turn ignition OFF. Probe the battery positive voltage terminal for the main relay armature at the underhood fuse block with a test light that is connected to a good ground. If the test light illuminates, go to next step. If test light does not illuminate, go to step  35 .
  20. Turn ignition ON, with engine OFF. Probe the relay coil control circuit terminal at the underhood fuse block with a test light that is connected to battery positive voltage. If the test light illuminates, go to step  23 . If test light does not illuminate, go to next step.
  21. Turn ignition OFF. Disconnect the negative battery cable at the battery. Disconnect the underhood fuse block electrical connector that contains the main relay coil control circuit. Disconnect the ECM electrical connector that contains the main relay coil control circuit. Measure the resistance of the relay coil control circuit from the underhood fuse block electrical connector to the ECM electrical connector with a DVOM. If the resistance measures greater than 5 ohms, go to step  34 . If the resistance does not measure greater than 5 ohms, go to next step.
  22. Test the main relay coil control bus bar circuit of the underhood fuse block for a high resistance or an open. Did you find a high resistance or an open? If yes, go to step  35 . If no, go to step  31 .
  23. Turn ignition OFF. Connect a 20-amp fused jumper wire between the battery positive voltage circuit terminal of the underhood fuse block and the relay load circuit terminal of the underhood fuse block. Probe the following fuses with a test light that is connected to a good ground:
    • ENGINE CNTL 1 FUSE
    • ENGINE CNTL 2 FUSE
    • ENGINE CNTL 3 FUSE

    If the test light illuminates on at least one test point of each fuse, go to next step. If test light does not illuminate on at least one test point of each fuse, go to step  35 .

  24. Measure the resistance from terminal No. 85 of the relay to terminal No. 86 using a DVOM. If the resistance measures 70-110 ohms, go to next step. If resistance does not measure 70-110 ohms, go to step  36 .
  25. Measure the resistance from terminal No. 30 of the relay to terminal No. 87 using a DVOM. If the resistance measures 8 ohms, go to next step. If resistance does not measure 8 ohms, go to step  36 .
  26. Measure the resistance from terminal No. 30 of the relay to terminal No. 85 using a DVOM. If the resistance measures 8 ohms, go to next step. If resistance does not measure 8 ohms, go to step  36 .
  27. Measure the resistance from terminal No. 85 of the relay to terminal No. 87 using a DVOM. If the resistance measures 8 ohms, go to next step. If resistance does not measure 8 ohms, go to step  36 .
  28. Measure the resistance from terminal No. 86 of the relay to terminal No. 87 using a DVOM. If the resistance measures 8 ohms, go to next step. If resistance does not measure 8 ohms, go to step  36 .
  29. Connect a 20-amp fused jumper wire from the battery positive cable at the battery to relay terminal No. 85. Connect a jumper wire from the negative battery cable to the relay terminal No. 86. Measure the resistance from terminal No. 30 of the relay to terminal No. 87 using a DVOM. If the resistance measures more than 3 ohms, go to step  36 . If resistance does not measure 3 ohms, go to next step.
  30. Test for an intermittent and for a poor connection at the main relay location on the underhood fuse block. Did you find a poor connection? If yes, go to step  35 . See INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.0L SATURN "L" SERIES article.
  31. Test for shorted terminals and poor connections at the ECM electrical connector. Did you find and correct a poor connection? If yes, go to step  38 . If no, go to step  37 .
  32. Repair the short to ground in the relay coil control circuit between the underhood fuse block and the ECM. After repair is complete, go to step  38 .
  33. Repair the short to voltage in the relay coil control circuit between the underhood fuse block and the ECM. After repair is complete, go to step  38 .
  34. Repair the high resistance or an open in the relay coil control circuit between the underhood fuse block and the ECM. After repair is complete, go to step  38 .
  35. Replace the underhood fuse block. After replacement, go to step  38 .
  36. Replace the main relay. After replacement, go to step  38 .
  37. Replace the ECM. See ENGINE CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION - SATURN "L" SERIES article. After replacement, go to next step.
  38. Reassemble the vehicle as necessary. Replace any open fuses. Clear any DTCs with a scan tool. Start the engine. Operate the vehicle in order to verify the repair. Did you correct the condition? If yes, go to next step. If no, see ENGINE CRANKS BUT DOES NOT RUN under NO START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 3.0L SATURN "L" SERIES article.
  39. Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 3.0L SATURN "L" SERIES article. If no, system is okay.
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