C0663Left 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
- Here the second left rear speed signal drops out for moments or jumps, without a lasting circuit fault. No public service data describes the code, so diagnosis has to follow the sensor principle. NXP's application note on magnetoresistive speed sensors warns that outside magnetic fields add to the measuring field: motors, relays and even wires carrying large currents close by can shift the signal far enough to lose pulses, and very strong fields can permanently change the magnet built into the sensor. On many cars the encoder is a magnetised ring in the wheel bearing seal; NTN-SNR points out that a magnetic screwdriver can erase its poles, which leaves gaps in the pulse train. C0663 also appears in GM's PIP5094 list, but only as an old, unrelated GM number.
- What you may notice
- Warning comes and goes, often on rough roads
- Brief, unexpected stability or ABS interventions
- Likely causes
- LikelyLoose contact in plug or harness that opens on bumps
- PossibleEncoder ring partly demagnetised or damaged
- RareInterference from nearby motors or high-current cables
- 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.