C05D4Brake Master Cylinder Piston Position Sensor Calibration Not Learned
- Generic OBD-II code · Chassis
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- No valid zero calibration exists for the master cylinder piston travel sensors. GM's integrated controller stores the end-of-line zeroing of its pedal travel sensors in non-volatile memory and reloads it each drive; C05D4 sets within 10 ms after start if the stored status shows the learn failed. GM lists sensor electrical faults, a moving vehicle or applied brake during calibration, and an offset too large, too small or unsteady, plus memory errors (19OBDG03D and 25OBDG04B, Type A with MIL). Hitachi learns stroke sensor zeros only with no brake request and discards a run that is interrupted. After replacing the brake unit, perform the calibration with a scan tool on a stationary vehicle. C05CC/C05CF cover offsets learned but out of limit.
- What you may notice
- Malfunction indicator lamp and brake warning after start
- Brake system in reduced mode until calibrated
- Likely causes
- LikelyZeroing not done after replacement of the brake unit
- PossibleCalibration disturbed by vehicle movement or pedal input
- PossibleSensor offset too large, too small or unsteady
- RareMemory error in the brake control module
- Repair
- Medium · Usually a job for a workshop.Typical cost: €80 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.