OBD-II code · Chassis
C05B4 Brake Booster Temperature Sensor C Circuit High
Brake booster temperature sensor C signal voltage above expected range. Boost control tracks commanded vs. actual manifold pressure; persistent deviation means wastegate, vanes, hose or actuator are not delivering the requested pressure.
Is it safe to drive with C05B4?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelySignal wire shorted to battery
- Less likelyConnector pins corroded - high contact resistance
- Less likelySupply wire pinched against B+ source
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–4 h
- Emissions test
- Usually unaffected
- Parts involved
- Brake Booster Temp Sensor C
Related codes
- C057ABrake Booster Temperature Sensor B Circuit High
- P25C7Brake Booster Temperature Sensor A Circuit High
- C05B1Brake Hydraulic Circuit D Leak
- C05B2Steering Wheel Angle Sensor Signal - Yaw Rate Sensor Signal Correlation
- C05B3Brake Booster Temperature Sensor C Circuit Low
- C05B5Brake Booster Temperature Sensor C Circuit/Open
- C05B6Brake Booster Temperature Sensor C Circuit Range/Performance
- C05B7Brake Booster Temperature Sensor C Circuit Intermittent/Erratic
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.