C0021
ABS Pump Motor Circuit Range/Performance
The pump motor responds, but its current draw or run time is outside the expected range. The control module suspects mechanical wear or hydraulic blockage.
- Check engine light: Not always
- Emissions related: No
- Repair difficulty: hard
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
Common causes
Ordered by how often each turns out to be the cause.
- Pump worn, low deliveryCommon
- Hydraulic block contaminated with brake fluid debrisPossible
- Sensor element aged beyond calibration windowLess likely
Parts involved
- ABS Pump Motor
- ABS Hydraulic Block
- ABS Control Module
C0021 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.