Chassis, generic

C0661 Left Rear Wheel Speed Sensor B Circuit Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

With C0661 the second left rear speed signal sits below the lowest level an intact sensor ever outputs, typically because the signal lead touches ground or the sensor feed has collapsed. No carmaker documents this code. What normal looks like is shown by a Motor magazine measurement on Honda sensors: a healthy unit switches cleanly between about 0.70 V and 1.40 V with a 50 % duty cycle, and a pickup magnet held against the sensor tip makes it switch. A level that stays below the lower band therefore points to wiring rather than to the encoder. Rear wheel speeds matter beyond ABS: in an HL Mando design the electric parking brake on the rear wheels uses them to calculate slip and backs off before a wheel locks during an emergency stop.

Likely causes

Signal lead chafed through and touching ground
Sensor supply pulled down, e.g. by water in the plug
Sensor B shorted internally

Symptoms

  • Warning for brake or stability system shortly after start
  • Emergency braking support of the electric parking brake may be restricted

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–450
Time0.5–2 h

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

Parts involved

lr wss bsensor wiring

Related codes

C065FC0662C050EC0668

References: motor.com, patents.google.com.