C05CABrake Master Cylinder Piston Position Sensor A Circuit Voltage High
- Generic OBD-II code · Chassis
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- Channel A of the travel sensor at the master cylinder input rod reports a signal beyond its upper limit. In GM's booster-type brake modules this channel is a linear position sensor (LiPS) that talks to the EBCM digitally over SENT, so the high error is a message from the sensor itself: the Cadillac XT4 table in 19OBDG03D reacts within 0.033 s on the fast channel, 23OBDG07 and 25OBDG03B after 0.96 s on the slow channel, Type A with MIL. Line shorts and lost messages are filed under separate network codes there. Continental describes pedal modules that read travel with two sensors so one bad channel can be identified. Check the sensor connector and supply before replacing the booster assembly. C05CB is the low counterpart.
- What you may notice
- Malfunction indicator lamp plus brake warning on GM models
- Reduced brake assist or changed pedal feel
- Likely causes
- LikelyPosition sensor A reporting out-of-range high internally
- PossibleSupply voltage of the sensor out of tolerance
- RareSensor magnet or input rod out of position
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.