C05CEBrake Master Cylinder Piston Position Sensor B Circuit Voltage Low
- Generic OBD-II code · Chassis
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- Here the second, PWM-coded output (channel B) of the piston travel sensor stays permanently low. GM's XT4 brake module and the later 23OBDG07 and 25OBDG03B tables interpret a constant low level for 0.2 s as the signal line shorted to ground, Type A, one trip, MIL. Because a PWM line at 0 V also results when the sensor loses its supply or ground, a dead channel B together with a working channel A suggests a wiring fault close to the second output, while both channels failing hints at the shared supply (C05D1). The module can usually still brake with channel A, but with less redundancy. Inspect the harness at the booster for crush or water damage before condemning the unit. C05CD is the stuck-high case.
- What you may notice
- Malfunction indicator lamp, brake system warning
- Possibly reduced assist or regeneration off
- Likely causes
- LikelyPWM signal line shorted to ground
- PossibleSensor channel B without supply or ground
- PossibleOutput stage of channel B failed low
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.