C0784
Trailer Brake Force Sensor Circuit Malfunction
The integrated trailer brake controller has detected an electrical fault in the brake force sensor circuit. Proportional trailer brake control is disabled — the controller defaults to a manual or fixed-gain mode.
- Check engine light: Not always
- Emissions related: No
- Repair difficulty: medium
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.
- Trailer brake force sensor failedCommon
- Wiring or connector faultPossible
Parts involved
- Trailer Brake Controller
- Brake Force Sensor
- Sensor Wiring
C0784 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.