What it means
Left Rear Wheel Speed Sensor B Intermittent/Erratic: the signal is intermittent or erratic. 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 rear wheel speed sensor B supplies a changing signal that the ABS control module monitors for wheel-speed and stability functions. This code sets when that signal becomes intermittent or erratic rather than remaining consistent, commonly because vibration disrupts a loose or oxidized connection.
Common causes
Most likely first.
- Connector loose or oxidized
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
How to diagnose it
- Review freeze-frame data and watch all four wheel-speed readings live, noting whether left rear sensor B drops out over bumps or during turns.
- Inspect the left rear sensor B connector for looseness, oxidation, or terminals that do not grip securely.
- Follow the harness and check for routing against a vibrating part, chafing, or strain near the suspension.
- With live data displayed, gently move accessible sections of the harness and connector to see whether the left rear reading changes.
- If the external connection is sound, test sensor B and the ABS module circuit for intermittent continuity using the manufacturer's procedure.
Common fixes
- Reconnect and secure a loose left rear sensor B connector.
- Clean serviceable oxidized terminals and restore proper terminal contact.
- Reroute and secure the harness away from vibrating or rubbing components.
- Replace a sensor or harness section only if testing reproduces an internal intermittent fault.
Can I keep driving?
The warning may come and go, but ABS and stability or traction control may stop working when the signal drops out. Drive cautiously, especially on wet or loose surfaces, and avoid relying on those systems until the fault is fixed.
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.