Wheel Speed Sensor Readings (VIDEO)

Wheel Speed Sensor Readings (VIDEO)

What could intermittent or erratic wheel speed sensor codes mean for wheel bearings? Sponsored by BCA Bearings by NTN.


A customer comes into your shop. They say that their ABS light is on and it usually comes on after one or two minutes of driving. You scan the vehicle and there are codes for a wheel speed sensor that say either intermittent or erratic. These can vary depending on the manufacturer and the type of code. What do these codes and that customer symptom have to do with the wheel bearing? Well, the reality of it is on most modern vehicles, the encoder, tone ring, or reluctor is part of the wheel bearing hub unit or part of the inboard seal on most wheel bearings on late model vehicles.

When this is there, well, when the bearing has in play, run out, or other issues, that tone ring can become unseated and it changes the air gap for the sensor. When the air gap changes for the sensor, this changes the signal or wave form coming back to the hydraulic control unit for the ABS. If it cannot get a consistent signal, it’s going to set that code.

Does it really matter? It’s just a land one wheel? Yes, because those systems actually check the four wheels, and if it sees behavior that is erratic or not normal, it sets that code. So how do you test to see if it actually is the hub unit? If you’re dealing with an active wheel speed sensor, it means that this seal actually has magnets that alter polarity going back and forth, back and forth, so it’s able to sense those magnets going by the wheel speed sensor head. When this happens, it registers the speed of the wheel or a degree of movement.

If you’re dealing with an older style passive wheel speed sensor, in those cases, you’re actually dealing with AC voltage being generated by a magnetic wheel speed sensor and window pans inside of something around the axle or part of the hub itself. In those cases, that sensor does not become active until the vehicle reaches five to seven miles per hour. But active is what you’re going to be dealing with on a lot of late model vehicles.

How do you test this? Well, you can use a scope. You can also use your scan tool to look at the different speeds and compare all four wheel speeds to see if something drops out when you’re making a corner or a turn, and this will confirm that there might be an issue with the hub unit. After that, perform a visual inspection. Take the wheel and make sure that there’s no in play. Then if possible, and you may have to remove the axle, look at the hub unit on the vehicle when it’s attached to the knuckle. If you see large pieces of debris stuck to it, try cleaning it and then going for a test drive. But if this seal is broken out of the lip, it needs to be replaced. There’s no way you can service just the seal.

Just keep that in mind when you’re dealing with one of these vehicles and a customer complaint that their ABS light is on and an erratic or intermittent wheel speed sensor code. I’m Andrew Markel. Thank you very much.

This video is sponsored by BCA Bearings by NTN

You May Also Like

Serpentine Service Typically Involves More Than Just The Belt

Your attention to belt condition will ensure systems are operating effectively. Sponsored by The Group Training Academy.

Certain components typically last a long, long time – your customer might not experience a serpentine belt replacement until their car or truck reaches 60,000-100,000 miles after it was installed at the factory during the vehicle’s assembly. 

Your service advisors should remember that, because the average age of vehicles today is in the 12-to-13-year range, many vehicles are being driven much longer than that. And light duty vehicles are being driven 12,000 to 14,000 miles a year (on average).      

Installing a Knuckle Hub Assembly

Addressing tough attachment points and ensuring proper torque is critical. Sponsored by GSP North America.

What is a Performance Brake Pad? (VIDEO)

There are engineering differences between race car and production vehicle brake systems. Sponsored by Akebono Brakes.

Belt-Driven Starter Generator Systems (VIDEO)

Fuel efficiency meets power with belt-driven starter generator systems. Sponsored by The Group Training Academy.

The Importance of Maintaining Belt Tension

Maintaining proper belt tension can enhance fuel economy. Sponsored by The Group Training Academy.

Other Posts

Audi Driver Assistance System Front-facing Camera Calibration

Joe Keene discusses how to calibrate the front camera on an Audi Q3 after the windshield was replaced.

Auto Pros On The Road Visit Detroit’s Jay’s Auto

Jay Salaytah meets the expectations of his customers and the needs of his employees. This video presented by Autolite.

Sealed Units Matter (VIDEO)

By sealing the joint, engineers can use better greases and materials to increase longevity. Sponsored by TRW.

Auto Pros Visit Interstate Auto Care, Madison Heights, MI

For Bill Nalu, business is more than fixing cars – it’s about connecting with people on a personal level.