C056BBrake Pressure Sensor A Intermittent/Erratic
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- C056B means the signal from brake pressure sensor A drops out or jumps for short moments instead of being steadily wrong. Ford's hybrid summaries (2015–2019) name two triggers: a checksum error in the digital data coming from the sensor for 70 ms, or a commanded control signal that does not show up at the sensor within 70 ms; the check runs only with a healthy sensor supply (no C056A). Ford's ABS module stores the same event as C0044. Saab's 2011 9-5 shows the consequence of an erratic pressure signal under its own code C0131: ABS, hill start assist, stability and traction control are disabled for the rest of the ignition cycle. Shaking the harness while watching live data helps find the loose contact.
- What you may notice
- ABS and stability lamps that come and go
- Stability control or hill start assist off until next start
- Regenerative braking reduced on hybrids
- Likely causes
- LikelyLoose or corroded contact in the pressure sensor connector or harness
- PossibleDisturbed digital sensor line, e.g. damaged shielding or poor ground
- PossibleSensor electronics failing intermittently, often in the hydraulic unit
- RareBrief dips in the 5 V sensor supply
- Repair
- Medium · Usually a job for a workshop.Typical cost: €40 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.