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Circuit/System Testing

NOTE:

Terminal and connector identifiers will be different depending on the individual control module being tested. Use Schematic Reference and Connector End View Reference to identify control module's connector, B+, ignition, ground, communication enable and serial data circuit terminals.

  1. Ignition OFF, disconnect the harness connector at the control module that is not communicating.
  2. Ignition OFF, test for less than 10 Ω between each ground circuit terminal and ground.
    • If greater than specified range, test the ground circuit for an open/high resistance.
  3. If equipped, ignition ON, verify that a test lamp illuminates between each B+ circuit terminal and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the control circuits of the control module for a short to ground. If the circuits test normal, replace the appropriate control module.
  4. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground.
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the control circuits of the control module for a short to ground. If the circuits test normal, replace the appropriate control module.
    5. NOTE:

    Only the high speed GMLAN modules have a serial data communication enable circuit OR an accessory wakeup serial data circuit, and the body control module is the output for these circuits. Refer to the control module schematics to identify which control modules have these circuits. If the control module that is not communicating does not have a serial data communication enable circuit OR an accessory wakeup serial data circuit, proceed to step 6.

  5. If equipped, ignition ON, verify that a test lamp illuminates between the communication enable circuit terminal OR the accessory wakeup circuit terminal and ground.
    • If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K9 body control module, for an open/high resistance or short to ground. If the circuits test normal, replace the K9 body control module.
  6. Ignition OFF, disconnect the harness connectors at the control module setting the DTC.
  7. Ignition OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 meters away from vehicle. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 Ω in each GMLAN serial data circuit between the non-communicating control module and the control module setting the DTC.
    • If greater than specified range, test the GMLAN serial data circuit for open/high resistance.
  8. If all circuits test normal, replace the control module that is not communicating.
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