P25C5
Brake Booster Temperature Sensor A Circuit Range/Performance
The booster temperature sensor reading is implausible relative to commanded assist or coolant temperature. The signal moves too slowly, sticks, or never reaches expected values during operation.
- 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.
- Sensor drift or contamination on the temperature elementPossible
- Sensor not seated properly against the booster motor housingPossible
- Sensor element aged beyond calibration windowLess likely
Parts involved
- Electric Brake Booster
- Temperature Sensor
P25C5 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.