OBD-II code · Chassis
C05B8 Brake Booster Motor A Position Sensor Supply Circuit/Open
Brake Booster Motor A Position Sensor Supply Circuit/Open: the circuit is open. 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 C05B8?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelySupply wire open
- Less likelyPin pushed back out of connector body
- Less likelyCracked solder joint inside the module or sensor
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
- Parts involved
- Booster Motor A Pos Sensor Supply
Related codes
- C05BCBrake Booster Motor B Position Sensor Supply Circuit/Open
- C05B5Brake Booster Temperature Sensor C Circuit/Open
- C05B6Brake Booster Temperature Sensor C Circuit Range/Performance
- C05B7Brake Booster Temperature Sensor C Circuit Intermittent/Erratic
- C05B9Brake Booster Motor A Position Sensor Supply Circuit Low
- C05BABrake Booster Motor A Position Sensor Supply Circuit High
- C05BBBrake Booster Motor A Position Sensor Supply Circuit Range/Performance
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.