C0663 code meaning
Left Rear Wheel Speed Sensor B Intermittent/Erratic
What C0663 means
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.
C0663 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of C0663
- Warning comes and goes, often on rough roads
- Brief, unexpected stability or ABS interventions
Common causes of C0663
- Most likelyLoose contact in plug or harness that opens on bumps
- PossibleEncoder ring partly demagnetised or damaged
- Less likelyInterference from nearby motors or high-current cables
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Lr wss bSensor wiringTone ring
What each part of C0663 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 63 | The exact fault in that area. |
What to do next
- Note C0663 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about C0663
What does C0663 mean?
C0663 means "Left Rear Wheel Speed Sensor B Intermittent/Erratic". Here the second left rear speed signal drops out for moments or jumps, without a lasting circuit fault. It is a generic code, so it means the same on every make.
Is it safe to drive with C0663?
Drive gently and only to a workshop. With C0663 the car can go into limp mode (reduced power) to protect itself.
Will C0663 fail an emissions test?
C0663 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is C0663 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will C0663 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.