Left rear ABS wheel speed sensor is reading about half the rotations as the rest

ARTURO B DELGADO

MEMBER
2012 BUICK REGAL
2.4L
4 CYL
2WD
AUTOMATIC
78,000 MILES

I purchased a descent scan tool which shows all the wheel sensors to compare when driving. The Left rear ABS wheel speed sensor is reading about half the rotations as the rest. I replaced the wheel bearing with a quality one about a year ago no issue until now. I did replace the sensor itself as well as cleaned the inside of the bearing where the magnets are but I am still getting the ABS and stability lights on the dash. Could it be there are two magnets in the bearing and only one is triggering the sensor? Thanks in advance for the help. Art

2 Replies

ARTURO B DELGADO

MEMBER
2 POSTS

Here are a few jpegs of the data. Dad was a certified mechanic and I’m a shady tree one. I work on industrial 3D Printers so know some mechanics. Thanks

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Tuesday, June 18th, 2019 AT 12:08 AM

STEVE W.

MECHANIC
13,017 POSTS

Welcome to 2CarPros. That looks like the magnet on the bearing has split. Not an uncommon problem. Even a hairline fracture will do it as it causes the data stream to drop out. An easy way to test if it's the sensor or the wiring is easy. Jack up the rear of the car so you can easily rotate the tires. Spin the left rear tire and see what it reads. Now spin the right rear. Note it's reading. Now disconnect the sensors and run a jumper lead from the right (good) sensor to the left sensor connector. Spin the wheel and see if the "left" speed now reads the same as it did when connected to the right side. If it does the wiring is good and the magnet is likely bad. If you have a scope you could connect it up to the sensors using a couple back probe contacts and see what that shows.