C0649Brake Pressure Sensor M Circuit/Open
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- The circuit of brake pressure sensor M, the twelfth in the series, has no continuity. Where so many pressure inputs exist, they are often not reachable from outside: WABCO notes that the two rear axle pressure sensors of its truck EBS are wired inside the axle modulator, so the cabling cannot be tested from outside and a fault means work on the modulator. Passenger-car units behave similarly; Actronics points out that the ATE MK60 carries its brake pressure sensor inside the unit, while some VW models use separate sensors near the master cylinder. External sensors, as on WABCO's trailer brake, take their supply from the modulator through a plug. No carmaker assigns C0649 or the letter M. Check plug and terminals first, then the unit.
- What you may notice
- Brake or ABS warning lamp on
- Electronic pressure control replaced by a fallback mode
- Likely causes
- LikelyLoose or corroded plug at an external sensor or at the modulator
- PossibleOpen in the internal wiring of the modulator or hydraulic unit
- RareBroken wire in the sensor harness
- Repair
- Hard · Usually a job for a workshop.Typical cost: €60 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.