C056A code meaning
Brake Booster Pressure Sensor Power Supply Circuit
What C056A means
Pressure sensors in the brake system are ratiometric parts fed with 5 V from the control module; HELLA's booster vacuum sensor, for example, is specified for 4.5–5.5 V and answers with 0.5–4.5 V. If that supply is missing or out of range, every reading is wrong, so C056A is checked before the sensor signals are judged. Ford's 2015–2019 hybrids use C056A exactly this way: the missing-calibration and erratic checks of the brake pressure sensors (C0560, C056B) only run when no C056A supply fault is present. No maker publishes a C056A threshold. Bosch notes the booster vacuum signal also governs the electric vacuum pump and start/stop. Expect brake assist and stability functions to be limited.
C056A at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C056A
- Brake or stability warning, often with further sensor codes
- Brake assist or electric vacuum pump control affected
- Stop/start inactive on some cars
Common causes of C056A
- Most likelyOpen or shorted 5 V supply wire to the sensor
- PossibleAnother sensor on the same reference pulling the supply down
- PossibleCorroded sensor connector
- Less likelyFaulty 5 V regulator in the control module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Brake booster pressure sensorSensor supply
What each part of C056A means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 6A | The exact fault in that area. |
What to do next
- Note C056A 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 C056A
What does C056A mean?
C056A means "Brake Booster Pressure Sensor Power Supply Circuit". Pressure sensors in the brake system are ratiometric parts fed with 5 V from the control module; HELLA's booster vacuum sensor, for example, is specified for 4.5–5.5 V and answers with 0.5–4.5 V. It is a generic code, so it means the same on every make.
Is it safe to drive with C056A?
Drive gently and only to a workshop. With C056A the car can go into limp mode (reduced power) to protect itself.
Will C056A fail an emissions test?
C056A 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 C056A to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will C056A clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.