C05AA code meaning
ABS Pump Motor Temperature Too High
What C05AA means
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.
C05AA at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor0.3 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C05AA
- ABS or stability control temporarily unavailable
- ABS or brake warning lamp on, often clearing after cooling down
Common causes of C05AA
- Most 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
- Less likelyModule ambient sensor or temperature model giving false values
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
ABS pump motorABS hydraulic unit
What each part of C05AA means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| AA | The exact fault in that area. |
What to do next
- Note C05AA and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about C05AA
What does C05AA mean?
C05AA means "ABS Pump Motor Temperature Too High". C05AA signals that the ABS return or high-pressure pump motor, or its switching stage, has become too hot. It is a generic code, so it means the same on every make.
Is it safe to drive with C05AA?
Drive gently and only to a workshop. With C05AA the car can go into limp mode (reduced power) to protect itself.
Will C05AA fail an emissions test?
C05AA is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is C05AA to fix?
Difficulty: hard. A typical repair takes 0.3 to 3 hours of work. This is a job for a workshop.
Will C05AA clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.