C0666Right Rear Wheel Speed Sensor B Circuit/Open
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- The second speed channel at the right rear wheel is open: a wire, terminal or the sensor itself no longer conducts. C0666 is not documented by any carmaker. Where the repair ends depends on the hub design. Schaeffler's wheel bearing brochure notes that some third-generation bearings carry all speed sensors inside the bearing unit, so an internal open there can mean replacing the whole hub assembly. The loss also affects the parking brake. A ZF patent on electric parking brakes handles a missing or implausible speed signal by closing the brake only while the switch is held and with a steady rise in force, so the car stays stable; full clamping follows only once maximum force is reached. Normal ABS often stays available through sensor A.
- What you may notice
- Warning for brake or stability system on every start
- Electric parking brake may only apply gradually while the switch is held
- Likely causes
- LikelyHarness or connector open at the right rear wheel
- PossibleSensor inside the hub bearing unit failed open
- RareInput stage for channel B in the brake module defective
- Repair
- Medium · Usually a job for a workshop.Typical cost: €60 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.