C0668 Right Rear Wheel Speed Sensor B Circuit Low
C0668 points to a channel reading that is too low for the second right rear sensor. No carmaker documents the code, so the limit is not public. With a current-output sensor the floor is easy to define: in NXP's KMI25 a constant source of about 7 mA runs the whole chip and is always present, even when no pulse is sent. A reading under that level means current is leaking past the sensor to ground or the sensor is not getting enough voltage. NXP's application note for the older KMI15 explains why this interface is chosen: the module turns the sensor current into a voltage across a load resistor, which keeps the signal robust over longer leads. A partly crushed lead along the rear suspension can produce exactly such a low reading.
Likely causes
Symptoms
- Warning lamp for ABS or stability control
- Redundant speed information at the right rear missing
Repair estimate
Typical range across vehicles; the real cost depends on what the testing finds.