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Home >> GMC >> 2021 >> Yukon AT4 >> Repair and Diagnosis >> Body & Frame >> Towing Systems >> TRAILERING Systems >> Diagnostic Information and Procedures >> DTC B1B58 >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the K68 Trailer Lamp Control Module. It may take up to 2 min for all vehicle systems to power down.
  2. Connect a test lamp between control circuit terminal 11 and ground, ignition ON.
    3. NOTE:

    The Center Stop Lamp scan tool control function can be found under the K219 Lighting Control Module.

  3. Verify the test lamp turns ON and OFF when commanding the Center High Mounted Stop Lamp ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Test circuit 820 for a short to ground.
      • 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. Test circuit 820 for an open/high resistance
      • 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.
    3. Replace the K219 Lighting Control Module.
    • If the test lamp is always ON 
    1. Test circuit 820 for a short to voltage.
      • If a short to voltage is found, repair the fault on the circuit.
      • Go to next step: If a short to voltage is not found.
    2. Replace the K219 Lighting Control Module.
    • Go to next step: If the test lamp turns ON and OFF 
  4. Replace the K68 Trailer Lamp Control Module.
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