C159C on GMC
Trailer brake control switch fault (Chevrolet, GMC)
Severity: Inspect soon
The Service Trailer Brake message means the electric trailer brakes may not work on that drive. Your truck brakes still work, but towing without trailer brakes lengthens stopping distance.
It gets more serious if:
- Stop: Do not tow if the trailer brakes are disabled and the trailer is heavy; stop in a safe place if the red brake warning light is on or the pedal feels different. Toyota's owner's manual, used as a general benchmark, treats a red brake light as a stop condition.
This page covers only what differs on GMC. For what C159C means, the ranked causes and the test order, see the C159C guide.
What's different on GMC
GMCYour car
2022–2023 · Sierra 1500
Supported by vehicle dataThe same GM bulletin covers the Sierra 1500, and a 2022 owner complaint reports trailer brakes disabled with C159C.
PIT5948B-GMCStatus unverified
Service Trailer Brake message with DTC C159C
2022–2023sierra-1500, yukon-xl · issued · NHTSA 10232813
Preliminary information: a Service Trailer Brake message shows with a trailer connected and C159C symptom 49 may be set for the trailer brake control switch. The NHTSA summary says GM engineering was working on it.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
Sources and review
- GM preliminary information PIT5948B: Service Trailer Brake message with DTC C159C
- NHTSA complaint ODI 11490095 (2022 Sierra 1500, C159C)
- NHTSA complaint ODI 11497601 (2022 Silverado 1500, C159C)
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error