ABS light won't clear - Code 520941 Left Rear Wheel Speed Sensor Erratic

Question

I have an ABS dash lamp and a CID 520941 FMI 2 fault showing on my display for the left rear drive axle. The traction control light is also staying on and I'm losing cruise control intermittently when I hit small bumps. It's driving me nuts because the sensor looks perfectly fine from the outside.

Jake Morrison · Accepted Answer

The issue was actually a loose wheel bearing allowing the hub to tilt slightly, which caused the tone ring to move away from the sensor. I replaced the sensor (Part #R955335) just to be safe, but the real fix was tightening the hub nut to spec and replacing the worn outboard bearing. Total cost for the sensor and bearing kit was about $340 plus 4 hours of labor.

torque_terry · Answer

Inspect the tone ring through the sensor hole. If there is a missing tooth or heavy rust buildup (jacking), the sensor will lose track of the count at highway speeds and throw that specific code.

Mike Reynolds · Answer

If you have a voltmeter, check the resistance at the sensor connector. You should see between 900 and 2000 ohms; if it's jumping all over while you wiggle the wire, the internal coil is shot.

fleet_chief_42 · Answer

Check the sensor gap first. Meritor WABCO sensors can be pushed in by hand until they touch the tooth wheel, and the first time the wheel spins, it sets the gap automatically.

ABS light won't clear - Code 520941 Left Rear Wheel Speed Sensor Erratic

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