C05BCBrake Booster Motor B Position Sensor Supply Circuit/Open
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- C05BC reports an interrupted supply for the position sensor of booster motor B. A B channel exists where the actuator carries a second motor or winding set, or measures its rotor angle twice for redundancy. No manufacturer documents C05BC publicly. Hyundai Mobis describes a brake actuator with a dual-winding motor whose two power modules are fed separately; when one is diagnosed faulty it is shut down and the full current command passes to the other. Hitachi Astemo pairs each sensor supply with its own angle and torque sensor and keeps the motor running on the healthy set. As in Denso's analysis, a broken feed drags the signal to 0 V. The usual result is a brake warning with reduced assist, while full failure of boosting is avoided.
- What you may notice
- Brake warning lamp, assist may remain partly available
- Reduced maximum assist or slower pressure build-up
- Likely causes
- LikelyBroken wire or pushed-back pin in the motor B sensor supply
- PossibleSecond sensor supply output in the control unit failed
- RareOpen inside the motor B position sensor
- Repair
- Hard · Usually a job for a workshop.Typical cost: €150 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.