OBD-II code · Chassis
C056A Brake Booster Pressure Sensor Power Supply Circuit
Fault on brake booster pressure sensor power supply circuit. 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 C056A?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelySupply wiring fault
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
- 0.5–2 h
- Emissions test
- Usually unaffected
- Parts involved
- Brake Booster Pressure Sensor
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.