Abs Malfunctioning


Old 05-04-07, 06:02 PM
Thread Starter
Join Date: Feb 2005
Location: Michigan
Posts: 335
Abs Malfunctioning

My abs kicks on when it should not be. The gear on the front passenger wheel that the abs sensor reads off of, is split. There is a very small gap, only about a millimeter. The other side does not have this, so I think it could be the problem, but im surprised that something so small could cause the abs to kick on. Could this be the problem?

The ring gear that the sensor reads the teeth on, (im not sure what its called) is wrapped around a spinning object (i think its the outer cv joint).

Is it possible to replace just the gear? Would I have to pull the whole wheel assembly apart? How would I fix this?

Car: 93 Grand Am SE, 2.3L SOHC, 34K original miles

Here is a link to a picture I pulled off the internet and used paint to try and show whats on my car.


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Old 05-04-07, 08:14 PM
HotxxxxxxxOKC's Avatar
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Yes, the sensor reads the teeth which is actually called a "tone wheel". Inspect the sensor wires, most of the time, road depris damages them.

Also, the gap between the sensor and the tone wheel is crucial. You will have to have a manual to tell you the spec.
Old 05-05-07, 12:02 PM
Thread Starter
Join Date: Feb 2005
Location: Michigan
Posts: 335
Thanks for the reply HotinOKC

Would the milimeter gap where the tone gear is split be enough to cause problems? The other side does not have a split, and the edges are rough, so I can tell its not supposed to be there. (as opposed to an intentional gap to put it on such as a piston ring) How would I replace the tone gear?
Old 05-05-07, 10:34 PM
Join Date: May 2007
Posts: 8
A millimeter is way more than enough of a gap to cause a problem. I have seen much smaller cracks on a tone ring cause ABS activation during normal stops. A FoMoCo engineer once explained it had to do with the magnetic flux at the crack and it appeared much bigger to the sensor than the eye.

As far as ring replacement, that is tricky. Most rings are heated, then pressed onto the outer CV joint and cool to an interference fit. They are easy to crack (the cast rings) during the install if you get rough with them. If it were mine, I would get a new outer CV with the ring already installed, or a complete rebuilt halfshaft if the price is right (I don't like to get dirty anymore).

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