Circuit/System Verification

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2016 GMC Sierra 3500 HD, 2016 GMC Sierra 2500 HD, 2016 GMC Sierra 1500, 2016 Chevrolet Silverado 3500 HD, and 2016 Chevrolet Silverado 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.

Ignition ON.
Verify that DTCs U1505, U1556, U2504, P2534, P2535, or any other communication DTCs are not set.
- If any of these DTCs are set
  Refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- If none of these DTCs are set
Verify the Service Trailer Brake System message is not displayed in the driver information center
- If the Service Trailer Brake System message is displayed and the customer's trailer is connected to the vehicle
1. Disconnect the customer's trailer.
2. Verify the Service Trailer Brake System message is not displayed in the driver information center.
  - If the Service Trailer Brake System message is not displayed after disconnecting the customer's trailer, the circuit fault causing the DTC to set is located in the customer's trailer wiring harness. This is not diagnosed in service information, nor is it covered by GM warranty.
  - If the Service Trailer Brake System message is displayed after disconnecting the customer's trailer
3. Refer to Circuit/System Testing.
- If the Service Trailer Brake System message is displayed and the customer's trailer is not connected to the vehicle
  Refer to Circuit/System Testing.
- If the Service Trailer Brake System message is not displayed and the customer's trailer is available
Verify the customer's trailer connection is recognized with a Trailer Connected message in the driver information center.
- If the Trailer Connected message is not displayed when the customer's trailer is connected to the vehicle
  Refer to Circuit/System Testing.
- If the Trailer Connected message is displayed when the customer's trailer is connected to the vehicle
All OK.