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Home >> GMC >> 2016 >> Acadia SL >> Repair and Diagnosis >> Engine Performance >> System >> Data Communication System >> Diagnostic Information and Procedures >> DTC U0100 - U02FF: Control Module U Code List >> Circuit/System Testing
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Circuit/System Testing

NOTE:

Use the schematic to identify the following:

  • Control modules the vehicle is equipped with
  • Control module locations on the low and high speed GMLAN serial data circuits
  • The control modules B+, ignition, ground, communication enable and serial data circuit terminals
  1. Ignition OFF, disconnect the harness connector at of the control module that is not communicating.
  2. Test for less than 10 Ω between each ground circuit terminal and ground.
    • If greater than the 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, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the 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, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the 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 K9 body control module is the output for these circuits. Refer to the control module schematics to identify which control modules have these circuits.

  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. NOTE:

    The following test step is only applicable to low speed GMLAN modules.

  6. Test for less than 4.5 V between each low speed GMLAN serial data circuit terminal and ground.
  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 5 Ω between the serial data circuit terminals and the appropriate X84 data link connector (DLC) terminal listed below:
    • Class 2 serial data circuit terminal 2
    • Low speed GMLAN serial data terminal 1
    • High speed GMLAN serial data terminal 6 or 14
    • Mid speed GMLAN serial data terminal 3 or 11
    • Chassis high speed GMLAN serial data terminal 12 or 13
    • If greater than the specified range, test the serial data circuit for an open/high resistance between the non communicating control module and a module setting the DTC or a serial data splice pack.
    8. NOTE:

    The following test step is only applicable to high speed GMLAN modules.

  8. Test for less than 130 Ω between each pair of high speed GMLAN serial data circuits.
  9. If all circuits test normal, replace the control module that is not communicating.
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