C05BBBrake Booster Motor A Position Sensor Supply Circuit Range/Performance
- Generic OBD-II code · Chassis
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- GM uses C05BB in the integrated brake control of 2019 models. There the processor generates two 5 V sensor supplies; each feeds one pedal travel channel plus one motor position channel. C05BB belongs to the second supply (PTS2 and MPS2), C05D1 to the first. GM sets it below 4.85 V or above 5.15 V for 100 ms, and also for an unsteady supply: every out-of-band sample adds 50 points and the fault matures at 800, so after 80 ms at the earliest; every good one subtracts 1, and the fault stays latched until ignition off. All three variants are Type A, MIL on the first trip. GM names a faulty motor position sensor, pedal travel sensor or circuit board as causes. GM thus books its MPS2 under a motor A code, though its MPS2 plausibility fault is C058E.
- What you may notice
- Check engine lamp and brake warning on the first trip (GM)
- Service brake assist message, hard pedal
- Fault remains until the ignition is switched off
- Likely causes
- LikelyDefective motor position sensor loading the shared supply
- PossibleDefective pedal travel sensor on the same supply
- PossibleFault on the brake control unit's circuit board
- RareIntermittent contact in the sensor supply wiring
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €200 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.