OBD-II code · Chassis
C05BB Brake Booster Motor A Position Sensor Supply Circuit Range/Performance
Brake Booster Motor A Position Sensor Supply Circuit Range/Performance: the signal is implausible or outside the valid range. The electric brake booster generates the braking assist; a motor or sensor fault can reduce or disable power-assisted braking. Safety-relevant.
Is it safe to drive with C05BB?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyConnector with high resistance
- Less likelySensor element aged beyond calibration window
- Less likelySensor mounting loose - signal damping
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–5 h
- Emissions test
- Usually unaffected
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Booster Motor A Pos Sensor Supply
Related codes
- C05BFBrake Booster Motor B Position Sensor Supply Circuit Range/Performance
- C05B8Brake Booster Motor A Position Sensor Supply Circuit/Open
- C05B9Brake Booster Motor A Position Sensor Supply Circuit Low
- C05BABrake Booster Motor A Position Sensor Supply Circuit High
- C05BCBrake Booster Motor B Position Sensor Supply Circuit/Open
- C05BDBrake Booster Motor B Position Sensor Supply Circuit Low
- C05BEBrake Booster Motor B Position Sensor Supply Circuit High
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.