Generic fault code
C05BD — Brake booster motor B position sensor, supply circuit: signal low
The control unit stores code C05BD when it detects this fault: “Brake booster motor B position sensor, supply circuit: signal low”.
Indicative severity: HighBrakes and stability
Reviewed by Daniel Morales, founder of Reprorace SL, on
What does code C05BD mean?
ABS, stability control and their sensors (wheel speed, brake pedal, pressure). With a fault here, ABS or stability control may be switched off.
- System
- C · Chassis
- Area
- Brakes and stability · Car system: Brakes, ABS and ESC
- Type
- Generic (SAE J2012 / ISO 15031-6): the same meaning on every make
- Indicative severity
- High. Diagnose as soon as possible: it may affect safety or cause damage (engine, catalyst, brakes).
What usually causes code C05BD?
- Short circuit to ground
- Loose or corroded connector, backed-out terminals
- Damaged, chafed or pinched wiring
The most likely causes come first. Only a check on the car confirms which one is yours.
What are the symptoms of code C05BD?
- ABS, ESP or brake warning lights on
- ABS and stability control switched off; normal braking usually still works
- On some cars, the speedometer or driver aids failing
These are the usual symptoms of this kind of fault: not all of them always appear, and sometimes you notice nothing.
Can I keep driving with code C05BD?
Better not, except when you really have to. This fault may affect safety or damage the engine, the catalytic converter or the brakes. See a workshop as soon as possible; if you must move the car, drive gently and only short distances. If the light flashes, the car loses power, makes unusual noises or the brakes or steering feel different, stop somewhere safe and call for assistance.
This is guidance only: only someone who checks the car can say whether it is safe to drive.
An indicative description of the code's generic meaning. Each manufacturer may give it a different meaning, conditions or tests: always follow its service information and your workshop's advice.
What you can do yourself
For this kind of fault
Keep a longer distance and avoid hard braking: without ABS the wheels can lock. If the red brake light comes on or the pedal feels different, stop and call for assistance.
Read the code and keep the report: with an ECO-LITE in the OBD socket you see it on your phone or computer, with the data captured when the fault happened.
Look for anything obvious: a loose connector, a disconnected hose, a fuel cap not closed properly or a low fluid level. Do not take apart anything you do not know.
Clear the code only after writing it down or after the repair. Clearing turns the light off, but it also deletes the freeze-frame data and the readiness monitors used at the inspection.
Drive normally for a few days and read the codes again. If the code comes back, the fault is still there: book the workshop and bring the report.
Read your car's fault codes on your phone
With an ECO-LITE in the OBD socket you see the codes in your account, with the data captured when the fault happened, and your workshop can check them remotely, always with your permission.
Related codes
- C05BABrake booster motor A position sensor, supply circuit: signal high
- C05BBBrake booster motor A position sensor, supply circuit: range/performance
- C05BCBrake booster motor B position sensor, supply circuit open
- C05BEBrake booster motor B position sensor, supply circuit: signal high
- C05BFBrake booster motor B position sensor, supply circuit: range/performance
- C05C0Brake pedal position sensor A: not learned
C05xx codes: wheel, steering and acceleration sensors
In the glossary
Read more: Remote OBD diagnostics: what it is, how it works and what it can't do