OBD-II code · Chassis
C05AF Brake Booster Motor B Current Sensor Circuit Range/Performance
Brake Booster Motor B Current Sensor 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 C05AF?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelySensor reading drifted
- 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
- 1–4 h
- Emissions test
- Usually unaffected
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Booster Motor B Current Sensor
Related codes
- C0596Brake Booster Motor A Current Sensor Circuit Range/Performance
- C05ACBrake Blending Separation Valve Stuck Closed
- C05ADBrake Blending System Performance
- C05AEABS Pump Motor Calibration Not Learned
- C05B0Brake Hydraulic Circuit C Leak
- C05B1Brake Hydraulic Circuit D Leak
- C05B2Steering Wheel Angle Sensor Signal - Yaw Rate Sensor Signal Correlation
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.