C004DBrake System Pressure Slow Response
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- A performance code set when the brake system builds or changes hydraulic pressure more slowly than the control unit commands during an assisted or automated braking event. In electronically controlled brake systems the module commands a target pressure and watches the pressure sensor; if the measured pressure lags the demand beyond a calibrated time or rate it concludes the pump, motor, valves or hydraulic path cannot respond quickly enough. It is a plausibility and timing fault rather than a single electrical defect, and can be caused by air in the system, a weak pump, a sticking valve or a restriction. Automated braking and stability functions are limited and the brake or ABS warning lamp is set. The entry follows the SAE J2012 generic definition and electro-hydraulic brake control design.
- What you may notice
- Longer pedal travel or delayed assist
- Automated braking functions limited
- ABS or brake warning lamp on
- Likely causes
- LikelyAir in the hydraulic system or low fluid
- PossibleWeak pump or motor performance
- RareSticking valve or hydraulic restriction
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €150 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.