C066ARight Rear Wheel Speed Sensor B Intermittent/Erratic
- Generic OBD-II code · Chassis
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- C066A describes a second right rear speed signal that keeps dropping out or jumping. No carmaker documents it. Apart from loose contacts, the encoder deserves a close look. Schaeffler explains that many wheel bearings carry a multipole encoder just inside the seal: a ring magnetised in alternating poles that the sensor reads. NSK adds that this surface must not be pressed on during fitting and must be kept away from magnets and dirt. A ring with a cracked section, a spot of attracted metal swarf or a weakened pole produces a pulse train with gaps, which reads as an erratic speed rather than a dead channel. Such a ring cannot be repaired on its own when it is part of the bearing, so the bearing or hub has to be replaced.
- What you may notice
- Warning appears and clears again during a drive
- Speed of the right rear wheel jumps in live data
- Likely causes
- LikelyEncoder ring with metal swarf, cracks or weakened poles
- PossibleIntermittent contact in plug or harness
- RareWorn wheel bearing letting the encoder wobble
- Repair
- Medium · Usually a job for a workshop.Typical cost: €60 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.