What it means
Left Front Wheel Speed Sensor B Circuit Low: the signal voltage is below the expected 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 sends wheel rotation data to the brake control module for ABS and stability functions. This code sets when the electrical signal from that specific circuit falls below the module’s expected range, often due to a short to ground or poor connection.
Common causes
Most likely first.
- Signal wire shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
How to diagnose it
- Capture freeze-frame data and compare live left front sensor B speed with the other wheels to confirm whether its signal is low or absent.
- Inspect the left front sensor B connector and harness for corrosion, water, pushed-back pins, or insulation rubbed through to ground.
- Gently move the harness near the left front wheel while monitoring live data to check for a position-dependent low signal.
- Use the wiring diagram to check the left front sensor B signal circuit for a short to ground and test its connections as specified by the manufacturer.
- If the wiring is sound, inspect the sensor and tone ring or encoder and test the sensor output against the manufacturer's specification.
Common fixes
- Clean and secure corroded or loose left front sensor B connector terminals.
- Repair wiring chafed through to ground in the left front sensor B circuit.
- Replace a damaged connector or restore its seal against water entry.
- Replace sensor B if its output remains low with a verified circuit.
Can I keep driving?
ABS and stability control may be unavailable, and the speedometer may be affected. Allow extra stopping distance and drive cautiously, especially on slippery roads.
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.