C0727
Trailer Connector Circuit Malfunction
The chassis or trailer brake module has detected a fault in the trailer wiring connector — for example open lighting circuit or short to ground. Trailer brake and lighting functions may be unavailable.
- Check engine light: Not always
- Emissions related: No
- Repair difficulty: easy
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
Common causes
Ordered by how often each turns out to be the cause.
- Connector pins corroded or bentCommon
- Short or open in trailer wiringPossible
Parts involved
- Trailer Connector
- Trailer Wiring
- Trailer Brake Module
C0727 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.