C0664Left Rear Wheel Speed Sensor B Correlation
- Generic OBD-II code · Chassis
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- C0664 flags that the second left rear speed value disagrees with its reference speeds, although its circuit is sound. No carmaker publishes the comparison. Two patents show how a rear wheel can be cross-checked. Bosch uses the left rear wheel as its example of a failed or omitted sensor: the module estimates that wheel from the other three, for instance as the front average or as front left plus front right minus rear right, and checks the result against the gearbox output speed. A fault counts only when the deviation stays above a threshold for a set time. Ford relies on the differential: the mean of both rear wheels follows from the output shaft speed and the final drive ratio. A sensor that disagrees with such references gets flagged even though it still sends pulses.
- What you may notice
- Warning set after a longer drive, not at start
- Automated or redundant brake functions refused
- Likely causes
- LikelyDamaged or wrong encoder ring giving a false pulse count
- PossibleTyre of different size or heavily worn on the left rear
- RareSensor B losing pulses at high speed
- Repair
- Medium · Usually a job for a workshop.Typical cost: €60 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.