C056F code meaning
Brake Booster Travel Sensor Circuit Low
What C056F means
The travel sensor tells the booster control how far its input side has moved. On older vacuum boosters it followed the movable wall; on Bosch's iBooster a differential travel sensor measures the offset between the pedal-driven input rod and the motor-driven booster body, and the controller works to bring that offset back to zero. C056F means the signal sits below its valid band – typically a short to ground, a lost sensor supply or an open reference. No maker publishes a C056F threshold; GM, for instance, files its pedal travel sensors as master cylinder piston position sensors (C05CC, C05CF). Without this input the module cuts or limits electric assist, so the pedal gets hard while the base brakes keep working.
C056F at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C056F
- Hard brake pedal with clearly higher pedal force
- Brake system or stability warning lamp and a message to service the brakes
- Brake assist, automatic emergency braking or regenerative braking unavailable
Common causes of C056F
- Most likelyTravel sensor signal wire chafed through and shorted to ground
- PossibleMissing 5 V supply to the sensor, e.g. corroded connector pin at the booster
- PossibleInternal fault of the travel sensor, usually built into the booster assembly
- Less likelyDefective sensor input stage in the booster control unit
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Brake booster travel sensorSensor wiring
What each part of C056F means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 6F | The exact fault in that area. |
What to do next
- Note C056F 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 C056F
What does C056F mean?
C056F means "Brake Booster Travel Sensor Circuit Low". The travel sensor tells the booster control how far its input side has moved. It is a generic code, so it means the same on every make.
Is it safe to drive with C056F?
Drive gently and only to a workshop. With C056F the car can go into limp mode (reduced power) to protect itself.
Will C056F fail an emissions test?
C056F 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 C056F to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will C056F clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.