OBD-II code · Chassis
C0556 Brake Booster Pressure Sensor Performance
The brake booster vacuum or pressure sensor signal does not respond plausibly to engine vacuum or electric booster activity.
Is it safe to drive with C0556?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyVacuum leak in booster line
- PossibleVacuum pump weak
- Less likelySensor element aged beyond calibration window
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
- Often, with basic tools
- Typical labour
- 0.5–3 h
- Emissions test
- Usually unaffected
- Parts involved
- Brake Booster Vacuum Sensor, Vacuum Pump
Related codes
- C0553Longitudinal Acceleration Sensor Circuit Low
- C0554Longitudinal Acceleration Sensor Circuit High
- C0555Lateral Accelerometer Voltage Out of Range
- C0557Left Rear Wheel Speed Sensor A Incorrect Component Installed
- C0558Right Rear Wheel Speed Sensor A Incorrect Component Installed
- C0559Power Steering Control Module Range/Performance – Rear
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.