C0660 code meaning
Left Rear Wheel Speed Sensor B Range/Performance
What C0660 means
C0660 means the wiring of sensor B at the left rear tests good, yet its output fails to act like a wheel speed: it may vanish at speed, jump or show an odd pulse pattern. No published service data defines the check. Mounting is a common reason. NXP's application note for magnetoresistive speed sensors explains that a sensor placed off-centre to its target delivers a weaker signal with extra offset, which shows up as a duty cycle well away from 50 %, while a tilt below about 4° hardly matters. The KMI25 even reports the problem itself: one bit of its AK protocol is set when the magnetic field becomes too weak for normal operation. GM's keyword list PIP5094 contains C0660 only as an older GM number with a different meaning.
C0660 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 C0660
- Warning only appears while driving, often above a certain speed
- Assistance functions withdrawn while ABS on sensor A continues
Common causes of C0660
- Most likelySensor seated off-centre or too far from its encoder
- PossibleEncoder ring worn, dirty or weakly magnetised
- Less likelySensor B degraded internally
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Lr wss bTone ring
What each part of C0660 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 60 | The exact fault in that area. |
What to do next
- Note C0660 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 C0660
What does C0660 mean?
C0660 means "Left Rear Wheel Speed Sensor B Range/Performance". C0660 means the wiring of sensor B at the left rear tests good, yet its output fails to act like a wheel speed: it may vanish at speed, jump or show an odd pulse pattern. It is a generic code, so it means the same on every make.
Is it safe to drive with C0660?
Drive gently and only to a workshop. With C0660 the car can go into limp mode (reduced power) to protect itself.
Will C0660 fail an emissions test?
C0660 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 C0660 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will C0660 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.