C0540Brake Pressure Sensor A Circuit/Open
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- General electrical fault in the circuit of brake pressure sensor A, typically an interrupted signal, reference or ground wire, or a connection with excessive resistance. No manufacturer documents this exact code publicly; Mitsubishi, for example, maps its sensor-A faults to C0044 and C053D to C053F instead. The function is well described elsewhere: a Bosch patent has the master-cylinder pressure sensor report to the ESC controller, which lights ABS and ESC lamps and changes to a reduced or off state on a fault, and Saab 9-5 (2011) service data checks the 5-V feed and the signal wire for opens within 0.1 s and then shuts off ABS, traction and stability control until the next ignition cycle. Ordinary braking remains. Low and high voltages have their own codes, C053E and C053F.
- What you may notice
- ABS and ESC warning lamps on
- Stability and traction control out of service
- Brake assist or hill-start assist missing
- Likely causes
- LikelyLoose, corroded or pushed-out pin at the sensor or brake module connector
- PossibleBroken signal, reference or ground wire
- RareInternal open circuit in the pressure sensor
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.