ABS constantly engaged
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ABS constantly engaged
Back again with another question.
I had the shop in town replace the front brakes and rotors on my 93 Bronco because I don't have a press to change out rotors. The job's done, but driving away from the shop, every time the brakes are pressed, the ABS engages and the pedal vibrates like mad.
It's back at the shop and they've replaced the left front sensor (no change) and pulled the ABS relay and the brakes act normally, just no ABS.
The Bronco did not have an ABS problem when I took it in.
Any thoughts?
I had the shop in town replace the front brakes and rotors on my 93 Bronco because I don't have a press to change out rotors. The job's done, but driving away from the shop, every time the brakes are pressed, the ABS engages and the pedal vibrates like mad.
It's back at the shop and they've replaced the left front sensor (no change) and pulled the ABS relay and the brakes act normally, just no ABS.
The Bronco did not have an ABS problem when I took it in.
Any thoughts?
Last edited by 1sscav; Sep 26, 2011 at 08:23 AM. Reason: added info
Lead Driver
Joined: Sep 2002
Posts: 9,182
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From: Gateway to the West
Not sure why a shop needed to swap rotors for you in the first place. You can drive out wheel studs with a lug on the end of each one and smack 'em with a mallet til they pop out. But that is neither here nor there.
The concern is less with the sensors and more that the tone rings BEHIND the spindle/hub are not bent, teeth damaged or covered in crud. The tone rings "tell" the sensor if a wheel is slipping. If the sensor cannot read the ring for some reason you get the symptoms you are experiencing. Neither the sensors nor the rings should have been touched during a rotor swap. The rings look like gears with tiny cogs. The sensors need a clear line of sight to the edge of the ring they are "reading". So clean sensors and rings are critical. The sensors actually "count" the teeth on the rings as they go by. The ABS computer knows how many teeth should pass the sensor at any given speed and if not enough of them do, the computer applies the ABS system to that wheel. Any condition that will cause the sensor to miscount teeth will cause problems.
The concern is less with the sensors and more that the tone rings BEHIND the spindle/hub are not bent, teeth damaged or covered in crud. The tone rings "tell" the sensor if a wheel is slipping. If the sensor cannot read the ring for some reason you get the symptoms you are experiencing. Neither the sensors nor the rings should have been touched during a rotor swap. The rings look like gears with tiny cogs. The sensors need a clear line of sight to the edge of the ring they are "reading". So clean sensors and rings are critical. The sensors actually "count" the teeth on the rings as they go by. The ABS computer knows how many teeth should pass the sensor at any given speed and if not enough of them do, the computer applies the ABS system to that wheel. Any condition that will cause the sensor to miscount teeth will cause problems.
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The rotors were chewed up a bit and since my daughter's taking the Bronco back to Albuquerque from Vermont, I just wanted everything running up to spec.
Thanks for the info in your reply, I'll get it over to the shop pronto.
Thanks for the info in your reply, I'll get it over to the shop pronto.
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