C05AAABS Pump Motor Temperature Too High
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- C05AA signals that the ABS return or high-pressure pump motor, or its switching stage, has become too hot. Few units have a sensor on the motor, so the temperature is usually modelled. A Kelsey-Hayes (now ZF) patent estimates the heat of the transistor that drives the pump from separate heating and cooling curves, starting from the module's ambient sensor; above a limit of about 90–150 °C (60–110 °C in deep cold) the pump is disabled until the estimate falls below a lower threshold, optionally with a warning lamp. Bosch describes a staged response in an electrohydraulic brake: as limits are passed, heat-producing functions are cut back down to the mechanical fallback. Long ABS or stability events, hot climates and a stiff pump favour it. No manufacturer publishes C05AA.
- What you may notice
- ABS or stability control temporarily unavailable
- ABS or brake warning lamp on, often clearing after cooling down
- Likely causes
- LikelyLong ABS, traction or stability interventions, e.g. on rough or slippery roads
- PossibleStiff pump or worn motor brushes raising current and heat
- PossibleHigh under-hood or ambient temperature
- RareModule ambient sensor or temperature model giving false values
- Repair
- Hard · Usually a job for a workshop.Typical cost: €0 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.