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Home >> GMC >> 2024 >> Sierra EV >> Repair and Diagnosis >> Body & Frame >> Towing Systems >> TRAILERING Systems >> Diagnostic Information and Procedures >> DTC C1114 >> Circuit/System Testing

Circuit/System Testing

    NOTE:
    • This procedure will only diagnose factory installed equipment and wiring up to the X88B Tow Vehicle Electrical Receptacle.
    • A circuit fault or damage with the customer supplied equipment is not diagnosed or supported by GM service information.
  1. Visually inspect the X88B Tow Vehicle Electrical Receptacle for the following:
    • Corrosion, moisture, or physical damage to the component housing
    • Harness connector corrosion, physical damage, terminal damage, terminal corrosion, or poor terminal tension
    • If any damage is found 

      Replace or repair the X88B Tow Vehicle Electrical Receptacle or connector as necessary.

    • Go to next step: If no damage is found 
  2. Ignition/vehicle off, all vehicle systems OFF, disconnect the connector at the X88B Tow Vehicle Electrical Receptacle.
  3. Verify a test lamp illuminates between ground circuit terminal B and B+.
    • If the test lamp does not illuminate. 
    1. Repair the open/high resistance on ground circuit or ground connection.
    • Go to next step: If the test lamp illuminates. 
  4. Connect a test lamp between signal circuit terminal C and ground, ignition on/vehicle in service mode.
    5. NOTE:

    Scan tool functions for trailer brake controls are under the K160 Brake System Control Module.

  5. Verify the test lamp intensity changes when adjusting the Trailer Brake Duty Cycle from a low percentage to a high percentage with a scan tool.
    • If the test lamp is always off and does not change intensity. 
    1. Test circuit 47 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 47 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 K67 Trailer Brake Control Module.
    • If the test lamp is always on and does not change intensity. 
    1. Test circuit 47 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 K67 Trailer Brake Control Module.
    • Go to next step: If the test lamp intensity changes 
    6. NOTE:

    The wiring of the trailer brake control circuit has been verified good to this point, recommend verifying the customers trailer brake system on the customers trailer is functioning properly before continuing.

  6. Replace the X88B Tow Vehicle Electrical Receptacle.
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