OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Chassis generic / SAE

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.

SystemChassis
Typegeneric / SAE
GroupC0
Range / number7 / 84

Possible causes

  • Trailer brake force sensor failed high
  • Wiring or connector fault medium

Symptoms

  • ABS warning light on
  • ESC/stability control deactivated
  • Possible reduced brake assist
  • Speedometer may behave erratically

Inspection / repair

  • Difficulty: medium
  • DIY: shop recommended
  • Estimated cost: 150–700 €
  • Estimated time: 0.5–2.5 h
  • Component: trailer brake controller
  • Component: brake force sensor
  • Component: sensor wiring

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication