C004CBrake Booster Motor A Position Sensor Exceeded Learning Limit
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- Set in an electric or electro-hydraulic brake booster when the position sensor of booster motor A reports a learned reference value outside the allowed adaptation range. The brake control unit learns the rest and travel positions of the motor-driven actuator so it can meter assist precisely; if the learned value drifts beyond the calibrated window the module can no longer trust the actuator position and stores this code. It points to a worn or shifted sensor, mechanical wear in the actuator or a learning routine that ran under wrong conditions rather than a hard electrical fault. Controlled brake assist is reduced or disabled and the brake or ABS warning lamp is set; conventional braking remains. No code-specific public bulletin was confirmed; the entry follows the SAE J2012 generic definition and electro-hydraulic brake actuator design.
- What you may notice
- Reduced or inconsistent brake assist
- Changed brake pedal feel
- ABS or brake warning lamp on
- Likely causes
- LikelyPosition sensor worn or shifted
- PossibleMechanical wear in the booster actuator
- RareLearning routine ran under wrong conditions
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €250 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.