What it means
Left Rear Wheel Speed Sensor - Mechanical: a mechanical fault is present — typically a damaged tone ring, excessive air gap, or loose mounting. Wheel-speed signals feed ABS, ESC, traction control and the speedometer.
How it works
The ABS module uses the left rear wheel-speed sensor to track that wheel's rotation for anti-lock braking and stability functions. It sets this code when the sensor's mechanical relationship to its tone ring appears faulty, such as from ring damage, an incorrect gap, or loose mounting.
Common causes
Most likely first.
- Damaged or worn tone ring
- Excessive sensor-to-ring air gap
- Loose or incorrect sensor mounting
- Wheel bearing or hub play affecting sensor gap
- Debris or damage interfering with the sensor and tone ring
Symptoms
- ABS warning light on
- Traction or stability control warning light on
- ABS or stability-control functions may be limited
How to diagnose it
- Read ABS freeze-frame data and compare live speeds from all four wheels at low speed to see whether the left rear reading drops out or differs from the others.
- Inspect the left rear sensor, its mounting, and the tone ring for looseness, impact damage, corrosion, or debris.
- Check the sensor-to-ring gap and tone-ring condition through a full wheel rotation, following the vehicle's inspection procedure.
- Check the left rear hub and bearing for play that could change the sensor gap as the wheel turns.
- If the mechanical parts are sound, inspect the sensor connector and harness, then test the sensor circuit against the manufacturer's specification.
Common fixes
- Clean debris from the left rear sensor and tone ring.
- Secure or correctly reseat the left rear sensor.
- Repair or replace a damaged left rear tone ring or hub assembly as applicable.
- Replace a left rear wheel bearing or hub with excessive play.
- Repair damaged left rear sensor wiring or replace a confirmed faulty sensor.
Can I keep driving?
Normal braking may remain, but ABS, traction control, or stability control may be limited, so allow extra stopping distance and drive cautiously, especially on slippery roads. Avoid relying on those systems until the fault is repaired; a loose or damaged hub or bearing also needs prompt attention.
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.