C0651 code meaning
Left Front Wheel Speed Sensor B Circuit/Open
What C0651 means
C0651 reports an open circuit at the second speed sensor of the left front wheel. Sensor B exists only where a wheel carries two independent speed signals, mainly in redundant brake systems for automated driving. Continental describes two layouts: two separate sensors per wheel, each wired to its own brake control unit, or one housing with two sensing elements, each with its own two-wire cable that can run to a different controller. On such two-wire sensors the signal rides on the supply current, and Allegro notes that the module can spot opens and shorts simply from the current drawn. No carmaker publishes C0651. Sensor A (C0500) usually keeps ABS working, but the redundancy is lost.
C0651 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 C0651
- Warning for brake or driver assistance system
- Automated driving or redundant brake functions unavailable
Common causes of C0651
- Most likelyBroken wire in the sensor B cable near the wheel
- PossiblePlug of the second channel loose or corroded
- Less likelySecond sensing element inside the sensor failed open
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Lf wss bSensor wiring
What each part of C0651 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 51 | The exact fault in that area. |
What to do next
- Note C0651 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 C0651
What does C0651 mean?
C0651 means "Left Front Wheel Speed Sensor B Circuit/Open". C0651 reports an open circuit at the second speed sensor of the left front wheel. It is a generic code, so it means the same on every make.
Is it safe to drive with C0651?
Drive gently and only to a workshop. With C0651 the car can go into limp mode (reduced power) to protect itself.
Will C0651 fail an emissions test?
C0651 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 C0651 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will C0651 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.