What it means
The brake control module monitors the temperature of brake booster motor A. It sets this code when the motor temperature exceeds its specified operating limit.
At a glance
- Usually lights the ABS or stability-control warning light
- The engine or gearbox may go into limp mode
How it works
Brake booster motor A supplies electric braking assist, and the brake control module monitors its temperature to prevent operation beyond its safe range. C05C2 is set when the reported motor A temperature exceeds the specified operating limit, whether from heat buildup, excess load, restricted cooling, or a faulty temperature signal.
Common causes
Most likely first.
- Extended or repeated braking causing heat buildup
- Brake booster motor working under excessive load
- Restricted motor cooling or airflow
- Temperature sensor or wiring fault
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
How to diagnose it
- Scan the brake control module for freeze-frame data and live motor A temperature to see whether the reading reflects a recent period of repeated braking or sustained load.
- Check for related brake booster or supply-circuit codes that could indicate motor A is working harder than expected.
- Inspect motor A and its cooling path for blocked airflow, debris, or visible damage.
- Check the temperature sensor wiring and connectors for damage or loose contacts that could distort the reading.
- If the temperature reading remains implausible after the motor cools, test the sensor circuit and motor operation using the manufacturer's procedure.
Common fixes
- Allow the motor to cool and avoid repeated heavy braking while checking whether the temperature fault returns.
- Clear debris or restore airflow around the motor A cooling path.
- Repair damaged temperature-sensor wiring or connector contacts.
- Repair or replace a motor A or temperature sensor confirmed faulty by testing.
Can I keep driving?
Brake assist may be reduced while the motor is overheated, so avoid steep routes, towing, and repeated hard stops until it cools and the fault is assessed. If assist remains weak or braking changes, stop safely and arrange recovery.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.