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Home >> Cadillac >> 2021 >> XT5 Sport >> Repair and Diagnosis >> External Pages >> Different car >> Section 771 (TRAILERING Systems) >> Diagnostic Information and Procedures >> DTC B1330 (Trailer Lamp Control Module) >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2023 GMC Sierra 3500 HD and 2023 GMC Sierra 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.
    NOTE:

    DTC B1330 may set due to an open fuse condition caused by the customers trailer lighting system.

  1. Ignition/vehicle OFF, disconnect the connector at the K68 Trailer Lamp Control Module.
  2. Verify a test lamp illuminates between ground circuit terminal 13 and B+.
    • If the test lamp does not illuminate 

      Repair the open/high resistance on the ground circuit or ground connection.

    • Go to next step: If the test lamp illuminates 
  3. Ignition on/vehicle in service mode.
  4. Verify a test lamp illuminates between each terminal and ground:
    • Terminal 1
    • Terminal 10
    • Terminal 38
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Test the B+ circuit for a short to ground:
      • Terminal 1 = Circuit 5840
      • Terminal 10 = Circuit 439
      • Terminal 38 = Circuit 5640
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found.
    2. Replace the open fuse and connect the K68 Trailer Lamp Control Module connector.
    3. Ignition on/vehicle in service mode.
    4. Verify the fuse does not become open.
      • If the fuse is open

        Replace the K68 Trailer Lamp Control Module

      • Go to next step: If the fuse is not open
    5. The customers trailer has an electrical fault causing the fuse to blow.
    • If the test lamp does not illuminate and the circuit fuse is OK 
    1. Test the B+ circuit for an open/high resistance:
      • Terminal 1 = Circuit 5840
      • Terminal 10 = Circuit 439
      • Terminal 38 = Circuit 5640
      • If an open/high resistance is found, repair the fault on the circuit.
      • Go to next step: If an open/high resistance is not found.
    • Go to next step: If the test lamp illuminates 
  5. Connect the K68 Trailer Lamp Control Module connector, ignition on/vehicle in service mode.
  6. Clear DTCs and verify DTC B1330 does not reset.
    • If DTC B1330 resets 

      Replace the K68 Trailer Lamp Control Module

    • Go to next step: If DTC B1330 does not reset 
  7. All OK.
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