C05BC code meaning
Brake Booster Motor B Position Sensor Supply Circuit/Open
What C05BC means
C05BC reports an interrupted supply for the position sensor of booster motor B. A B channel exists where the actuator carries a second motor or winding set, or measures its rotor angle twice for redundancy. No manufacturer documents C05BC publicly. Hyundai Mobis describes a brake actuator with a dual-winding motor whose two power modules are fed separately; when one is diagnosed faulty it is shut down and the full current command passes to the other. Hitachi Astemo pairs each sensor supply with its own angle and torque sensor and keeps the motor running on the healthy set. As in Denso's analysis, a broken feed drags the signal to 0 V. The usual result is a brake warning with reduced assist, while full failure of boosting is avoided.
C05BC at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C05BC
- Brake warning lamp, assist may remain partly available
- Reduced maximum assist or slower pressure build-up
Common causes of C05BC
- Most likelyBroken wire or pushed-back pin in the motor B sensor supply
- PossibleSecond sensor supply output in the control unit failed
- Less likelyOpen inside the motor B position sensor
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Booster motor b pos sensor supplyElectric brake booster
What each part of C05BC means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| BC | The exact fault in that area. |
What to do next
- Note C05BC and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about C05BC
What does C05BC mean?
C05BC means "Brake Booster Motor B Position Sensor Supply Circuit/Open". C05BC reports an interrupted supply for the position sensor of booster motor B. It is a generic code, so it means the same on every make.
Is it safe to drive with C05BC?
Drive gently and only to a workshop. With C05BC the car can go into limp mode (reduced power) to protect itself.
Will C05BC fail an emissions test?
C05BC is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is C05BC to fix?
Difficulty: hard. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will C05BC clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.