Service Trailer Brake Message With DTC C1114 And/Or C1112 - keywords connector module TBCM tow 7way wheel wire

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Some owners may comment of a Service Trailer Brake System message displayed on the DIC. When checking for DTCs a C1112 and/or C1114 will be set in the Trailer Brake Control Module (TBCM). This concern may occur with or without a trailer connected to the vehicle.

GM Engineering is attempting to determine the root cause of this type of failure and is requesting your assistance. Engineering is requesting to be contacted so they can gather information related to this concern. PRIOR to making contact with the engineer listed below, please provide as complete of an answer as possible for the following questions:

DEALERSHIP

1. Dealership name and location
2. Main Contact Person and Phone Number

IMMEDIATE DIAGNOSIS

1. Which trailer brake faults are currently set on the vehicle? (C1112, C1114, both)
2. Are there any trailer brake faults set in history?
3. Is the "Service Trailer Brake" message illuminated in the DIC?
4. What is the gain setting when the fault is active?
5. Are any fuses blown related to the C1112 or C1114 faults?
6. Does fault occur only when vehicle brake applied with trailer connected?
7. Does fault occur only when vehicle brake applied with NO trailer connected?
8. Does the fault return if cleared?
9. If the concern can be duplicated, please obtain a center trigger Tech 2 or VDR snapshot of the event.

CUSTOMER/TRAILER RELATED INFORMATION

1. Has the customer experienced the same fault before?
2. Has a trailer ever been connected to the vehicle?
3. Did the fault occur with or without a trailer connected?
4. If a trailer was connected, list trailer details:

•	Brand Name

•	Electric or Electric Over-Hydraulic Brakes

•	Number of Axles/Magnets

•	Electrical loads (lights, fans, etc.)

5. Was the "Trailer Connected" message ever present with no trailer connected?
6. What time of day did the fault occur?
7. What was the outside temperature when the fault occurred?
8. What was the customer gain setting when the fault occurred?
9. Was the gain setting ever changed by customer?
10. Was the truck parked with the engine running for an extended period of time?
11. Was the customer near any airports or high tension power lines when the fault occurred?

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GM Engineering contact information:

Contact the individual below to review the responses to the questions above:

If necessary, leave a message with the following information:

Important: If the engineer is unable to return your call within one (1) hour, proceed with diagnosis and repair according to SI.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.