Sporadic ABS Issue?

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Recently my wife's 04 Grand Prix has developed an issue where the ABS system will ramdomly go off when braking. This even happens when comming to a slow stop on dry pavement. Right now it is very ramdom so it doesn't happen everytime you are breaking but it happens enough that it is a concern. I have inspected the pads and rotors and both look fine from what I can tell but I am not a mechanic. No idiot lights are comming on indicating an issue or that the ABS system is being deployed but from the sound and feel I am pretty sure it is the ABS system. In my other vehicles the ABS idiot light goes off when the ABS system is active which is not happening in my wife's car which I find interesting.

The car is still under an extended warranty for about another 5k miles so if the issue is something faulty with the ABS system I would like to get it fixed under warranty if possible. However, before I take it in I would like help figuring out as much about the issue as I can so that the right thing gets fixed. The last time my wife's car needed work I did not have time to look at the issue so I had her just take it in and describe the problem and they ended up fixing the steering column in the vehicle based on a TSB but when she brought it back home the problem was still there so when I got time to look at it I immediatly found out that it was a blister that developed in the tire. IMO they should have been able to diagnose the problem if they would have actually drove the car and inspected it properly. So I don't want to pay my deductible for something that isn't the problem if I take the car in to be fixed.

Anyone who may know what could be causing this or has come accross this same sporadic ABS issue I would appreciate any input.
 
I would see if your car stored a diagnostic code.

What causes you to suspect a problem? It is not obvious what it means to have ABS system will randomly go off when braking. Does that mean you feel a pulsing when you think that is inappropriate, or that the system fails to pulse when you think it should?
 
Originally Posted By: punisher
Bent/cracked toothed ring.


Yep, if the exciter ring is badly rusted where the teeth aren't consistent, you'll get random ABS activation when the optical senor reads the bad spot.

Joel
 
Originally Posted By: Carbon
I would see if your car stored a diagnostic code.

What causes you to suspect a problem? It is not obvious what it means to have ABS system will randomly go off when braking. Does that mean you feel a pulsing when you think that is inappropriate, or that the system fails to pulse when you think it should?


The ABS system is comming on when it shouldn't.
 
When the sensor got dirty on my truck the abs would randomly activate when I was close to a stop.
 
Originally Posted By: punisher
Bent/cracked toothed ring.


+1 So the wheel speed sensor tells your car that 3 wheels are going at 30km/h and one wheel at 0 km/h.

Check wheel speed sensor and the toothed ring.
 
The "toothed ring" might be sealed w/in the wheel bearing/hub assembly on this vehicle.
 
Last edited:
Agreed on the wheel sensor. I've seen some that were entirely random and some that would always trigger the ABS at a set speed like my friend's BMW at exactly 10mph.
 
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