ABS light illuminates when I hit a crack, pot hole or rough road

[nadodude111]

ABS works fine until I hit rough road or a rack in the road. The light comes on with key in 2 then turns off when engine is started. This means the sensors are working until I hit a bump so I assumed the test to check each sensor wouldn’t work. I tried it tonight by unplugging all of them but one and trying that on each sensor to see if the light stays off but the light came on for all sensors.

What should I do next? Just replace all sensors since I can’t determine which one it is? Car is a 91 so it has the late model relay.

The light will turn off if I restart the car but what’s interesting is that I have to unbuckle my seat belt and open the door to get the light to turn off when I start the car. If I keep my seat belt on and don’t open the door and restart the car, the light ABS just stays on.

really hate losing the ABS feature when inevitably hitting rough road. Pulling over and restarting the car has gotten old real quick. Any ideas?

[82eye]

first clean your abs rings. that's the most common cause of a flickering abs light. it simply defaults to regular braking. if that doesn't work then start chasing sensors. after that it could be electrical, relay, dme etc.
last and worst case is a failing abs pump.

[nadodude111]

82eye thanks for the suggestion. Is the ABS ring the cavity the speed sensor sits in? Any cleaning how tos or recs is appreciated.

thank you,

[82eye]

82eye thanks for the suggestion. Is the ABS ring the cavity the speed sensor sits in? Any cleaning how tos or recs is appreciated.

thank you,

it's a toothed ring on the hubs. it works the same as a cps. use a brass toothbrush sized brush to get at them. should be able to fit through the sensor holes, and probably get at them from the back as well.






for the record near 40 yr old abs is gonna be questionable at the best of times.

[nadodude111]

82eye you’re a genius like always - thank you! Cleaned and scrubbed the rings with brake cleaner and brush and fixed it. I’d probably cleaned the sensors twice and sprayed cleaner into the sensor cavity but never spun the hub and sprayed/scrubbed the ring all the way around.

For future reference: took the car for a test drive and within 5 feet the ABS light came on. Restarted car and the light came on again after driving a few feet. Did the single sensor test and they all passed. Plugged them all back in and the light turned off and stayed. On the drive the ABS was activating whenever I touched the brakes and the pedal was stiff. I pushed thru the stiffness and you could feel the pedal and braking power open up - the abs clicks stopped after that. Am sure the liquid brake cleaner was confusing the sensors and pump.

[82eye]

hope the easy fix wins. it's nice when it's not expensive either.

[nadodude111]

82eye ok so the problem still exists. After cleaning them, I drove the car over the speed bump that 100% always sets the light off and the light didn’t come on, hence why I thought I fixed it. But now the abs light comes back on with every crack or bump in the road. Should I try cleaning the sensors and rings again or is this something else?

[82eye]

it's gonna be something else.

[jbontke]

The ABS relay under the dash (on top pf ABS box) has a "fuse" or piece of wire in it that pops when overloaded. I wonder if its broke and loses connection when jarred? Here is a video that reverences the wire and how to "fix" it: https://www.youtube.com/watch?v=S-49okhvhks