What it means
Left Front Wheel Speed Sensor B Range/Performance: the signal is implausible or outside the valid range. Wheel-speed signals feed ABS, ESC, traction control and the speedometer.
At a glance
- Usually lights the ABS or stability-control warning light
- The engine or gearbox may go into limp mode
How it works
The left front wheel speed sensor B measures rotation at that wheel and sends the signal to the brake control module for ABS and stability functions. This code sets when the module judges that sensor’s signal implausible, outside its valid range, or inconsistent with wheel rotation.
Common causes
Most likely first.
- Tone ring damaged or contaminated
- Sensor element aged beyond calibration window
- Sensor mounting loose - signal damping
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
How to diagnose it
- Record freeze-frame data and compare live left front sensor B speed with the other wheel speeds while moving slowly in a safe area.
- Inspect the left front sensor B mounting and the tone ring or encoder for looseness, damage, contamination, or an uneven gap.
- Check the sensor face, connector, and harness for debris, impact damage, or wiring that can move against the wheel or suspension.
- Inspect the tone ring or encoder through a full rotation for damaged teeth, cracks, or contamination that could interrupt the left front signal.
- If the mechanical parts and wiring look sound, test sensor B’s output and mounting against the manufacturer's specification.
Common fixes
- Clean contamination from the left front sensor B or tone ring area.
- Secure the sensor B mounting and correct a loose or uneven fit.
- Repair damaged wiring or connector terminals at the left front wheel.
- Replace a damaged tone ring or encoder, or replace sensor B if its output is faulty.
Can I keep driving?
ABS and stability control may be disabled, and traction control may not operate correctly. Drive slowly and cautiously, especially on wet or loose surfaces, and avoid relying on these systems.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.