Chassis, generic

C0660 Left Rear Wheel Speed Sensor B Range/Performance

Check engine lightUsually off
EmissionsNot relevant
Drive cycleRequired
Limp modePossible

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.

Likely causes

Sensor seated off-centre or too far from its encoder
Encoder ring worn, dirty or weakly magnetised
Sensor B degraded internally

Symptoms

  • Warning only appears while driving, often above a certain speed
  • Assistance functions withdrawn while ABS on sensor A continues

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–700
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

lr wss btone ring

Related codes

C065FC0663C0664C050DC0667

References: nxp.com, nxp.com, static.nhtsa.gov.