C058CBrake Booster Motor B Position Sensor Circuit Low
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- C058C applies when the motor B position signal sits below its lower limit – usually a sensor line shorted to ground, a missing sensor supply or a damaged sensor element. No manufacturer publishes this code; GM limits its documented position checks to motor A, where C0588 trips in the XT4 module below 1,300 counts. The physics are the same on either side: Hitachi's resolver patent attributes a reading near 0 V to a ground short, and a vector-length check like the one Infineon specifies for its TLE5009 sine/cosine sensor exposes an amplitude that has collapsed. In a dual-winding booster as described by Hyundai Mobis, the inverter for winding B depends on this angle, so the module shuts that inverter down and relies on the remaining channel.
- What you may notice
- Brake warning lamp
- Assist may continue on one channel with reduced dynamics
- Likely causes
- LikelySignal line of sensor B shorted to ground
- PossibleSupply of sensor B missing or too low
- RareSensor element B or its magnet degraded, signal amplitude too small
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €2,800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.