What it means
Brake pedal position sensor B reference not learned — typically required after sensor or pedal replacement.
At a glance
- Usually lights the ABS or stability-control warning light
How it works
Brake pedal position sensor B reports pedal position to the brake control module, which uses the learned reference to interpret its readings. C05C1 is set when sensor B's reference has not been learned, commonly after sensor or pedal work or an interrupted calibration.
Common causes
Most likely first.
- Brake pedal position sensor B calibration or relearn not completed
- Sensor, pedal, or related component replaced without initialization
- Calibration interrupted or performed under unsuitable conditions
- Low system voltage during the relearn
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
How to diagnose it
- Scan the brake control module for related codes and live readings from brake pedal position sensor B to confirm its reference is missing.
- Check the service history for recent work on sensor B, the pedal, or related brake components that may have left initialization incomplete.
- Inspect sensor B's connector and wiring and check system voltage for a condition that could have interrupted relearning.
- If the sensor and connections are sound, perform the manufacturer-specified sensor B relearn under the required conditions.
- Clear the code and confirm the module recognizes sensor B's reference and the warning does not return.
Common fixes
- Complete the manufacturer-specified brake pedal position sensor B relearn.
- Restore stable system voltage and repeat the relearn if low voltage interrupted it.
- Reconnect or repair sensor B wiring or connector faults found during inspection.
- Replace a faulty sensor or repair related components only if testing shows relearning cannot complete with sound connections.
Can I keep driving?
ABS and stability control may be unavailable and brake assist may be reduced, so drive only as needed to reach a safe place for inspection. Stop if braking feels abnormal and have the system checked before relying on its electronic assistance.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.