C0668 code meaning
Right Rear Wheel Speed Sensor B Circuit Low
What C0668 means
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.
C0668 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C0668
- Warning lamp for ABS or stability control
- Redundant speed information at the right rear missing
Common causes of C0668
- Most likelyCrushed or chafed lead leaking current to ground
- PossibleHigh contact resistance lowering the sensor voltage
- Less likelySensor B internal current source defective
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Rr wss bSensor wiring
What each part of C0668 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 68 | The exact fault in that area. |
What to do next
- Note C0668 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 C0668
What does C0668 mean?
C0668 means "Right Rear Wheel Speed Sensor B Circuit Low". C0668 points to a channel reading that is too low for the second right rear sensor. It is a generic code, so it means the same on every make.
Is it safe to drive with C0668?
Drive gently and only to a workshop. With C0668 the car can go into limp mode (reduced power) to protect itself.
Will C0668 fail an emissions test?
C0668 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 C0668 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will C0668 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.