P25C4
Brake Booster Temperature Sensor A Circuit
The temperature sensor monitoring the electric brake booster (iBooster, eBooster) returns no usable signal. Without temperature feedback the controller derates booster assist to protect the motor.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: hard
Symptoms
- Check engine light on
- Significant power loss / limp mode
- Possible blue or black smoke from exhaust
- Whistling or hissing sound from intake
Common causes
Ordered by how often each turns out to be the cause.
- Open sensor element or broken sensor wireCommon
- Corroded connector on the booster sensor pigtailPossible
Parts involved
- Electric Brake Booster
- Temperature Sensor
- Wiring Harness
P25C4 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.