C05CCBrake Master Cylinder Piston Position Sensor A Circuit Range/Performance
- Generic OBD-II code · Chassis
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- Channel A (GM calls it PTS1) delivers a travel value that is electrically valid but physically wrong. GM's integrated controller with pedal simulator, the vacuum-free design ZF supplies, checks three things: travel above 38 mm (normal input piston travel is about 25 mm, about 36 mm without boost), a change faster than 700 mm/s, and a learned offset beyond 2.5 mm, each 100 ms, Type A. In the XT4 booster module the zero offset with pedal released may not exceed 0.9 mm while driving and accelerating; 23OBDG07 and 25OBDG03B allow +1.1/-1.5 mm. Causes range from a failed sensor to a bent sensor rod or wrong mounting. C05CF is the same check on channel B, C05D0 compares both channels.
- What you may notice
- Malfunction indicator lamp and brake warning
- Changed pedal feel or reduced assist
- Brake lights may react inconsistently
- Likely causes
- LikelySensor A offset drifted beyond the learn limit
- PossibleDamaged travel sensor rod or mounting
- PossibleIntermittent signal line producing jumps
- RarePedal not fully returning (floor mat, return spring)
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.