What it means
Right 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 right rear Wheel Speed Sensor B reports wheel rotation to the brake control module for ABS, stability control, and traction control. The module sets C066A when this sensor's signal cuts in and out or changes erratically, often as the wheel or harness moves.
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
- Read freeze-frame data and compare live speeds from the right rear Sensor B with the other wheels to see when its reading drops out or jumps.
- Inspect the right rear Sensor B connector for looseness, oxidation, moisture, or pins that may lose contact under vibration.
- Trace the Sensor B harness and look for rubbing against a vibrating component, chafing, stretched sections, or poor routing.
- With a scan tool displaying live wheel speeds, gently move the connector and harness while the vehicle is stationary, following safe test procedures, and watch for dropouts.
- If the wiring and connections look sound, test continuity and circuit integrity while flexing the harness, then check the sensor and wiring against the manufacturer's specification.
Common fixes
- Reconnect and secure the right rear Sensor B connector; clean or repair corroded terminals as appropriate.
- Repair damaged Sensor B wiring and secure the harness away from vibrating or moving parts.
- Replace a sensor that fails testing against the manufacturer's specification.
Can I keep driving?
ABS and stability control may be unavailable while this fault is active, and brake assist may be reduced. Drive cautiously only if braking feels normal, avoid slippery roads and hard braking, and stop if braking behavior changes.
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.