C066FService/Park Brake Chamber Pressure Too Low
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- C066F reports chamber pressure below what the brake system needs. No maker documents this code. For the spring section the consequences are clear: inside Bendix's piggyback unit the main spring starts to apply the brake once its chamber pressure falls under 78 psi, so a leak or weak supply makes the brakes drag. UN Regulation 13 requires that the springs of a motor vehicle do not start acting above 80 % of the lowest normal pressure, and that the driver is warned when the feed to the spring chamber sinks far enough for the brake components to start moving. FMVSS 121 asks for a warning once the service reservoir falls below 60 psi. Haldex lets its trailer EBS monitor spring brake pressure through an extra 5 V sensor and light a lamp under a set limit.
- What you may notice
- Red brake or low-air warning, parking brake indicator flashing
- Brakes dragging or spring brakes applying on their own
- Likely causes
- LikelyLeaking diaphragm, chamber seal or supply line
- PossibleInsufficient reservoir pressure from compressor or dryer
- RarePark valve or relay valve not delivering full pressure
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.