05 Equinox brake question, any GM techs here? - Chevy Colorado & GMC Canyon
 
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post #1 of 7 (permalink) Old 01-20-2012, 08:09 AM Thread Starter
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05 Equinox brake question, any GM techs here?

Just thought I would ask, I know this is supposed to be a Colorado forum. My sisters Equinox, 1st year 2005, same year as my Colorado, just as you come to a stop the ABS pump runs, makes the buzzing noise, but does stop OK, so just an irritation sort of thing. Doesn't have any kind of warning light for the ABS. Doesn't do it every time she stops, but will do it on dry pavement.
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post #2 of 7 (permalink) Old 01-20-2012, 12:27 PM
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It sounds like there is something faulty with a speed sensor if ABS is kicking in. When the wheel stops rotating the ABS system becomes energized. It sounds like the system think the wheel has quit rotating. Has the vehicle been in an accident or had any repair work performed lately?
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post #3 of 7 (permalink) Old 01-20-2012, 06:52 PM Thread Starter
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Only thing I am aware of is she needed the engine replaced, put in a used engine IIRC. I wonder if a rear brake could be grabbing? Like I say though, it seems to stop fine otherwise.
Yeah I figured that the ABS thinks a wheel is locking so is applying abs. I sort of thought if a sensor was bad that it would throw a code, why would it fail like this only when coming to a stop?
I will wait and see what kind of feedback I get from her since I did the front brakes. I did tell my feelings about it after I did the front brakes and then noticed this problem, so maybe just knowing what it is will make her happy enough. If it was mine I'd want it fixed though. Too bad it all has to happen just when we get this crappy weather though.
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post #4 of 7 (permalink) Old 01-20-2012, 07:49 PM
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I don't know if a code would be thrown for ABS, because it's doing the job it's supposed to do. If anything, I would expect a brake light would illuminate on the dash if there was fault in the brake system.

It should only fail during stopping because that is when the ABS system is being energized. Honestly, I don't have any other ideas.

When you did the front brakes, did you damage the ABS line, or have any reason to remove the rotor? The ABS ring may not be seated properly if you have removed the rotor.

I think you would feel it if the rear was locking up, it should be pretty grabby if one of the brakes are out of adjustment. Are the rear brakes drums or disc? Drums, maybe you can try readjusting the shoes in the drums.
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post #5 of 7 (permalink) Old 01-21-2012, 03:05 PM Thread Starter
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The wheel speeds are being monitored at all times I believe, not just when the brakes are applied. So I would assume, if a sensor was bad and went down to "zero" rpms while driving, that there would be a code. It would be hard to believe that the sensor is failing only when almost stopped and causing the pump to run. That's why I am confused. Even the reluctor ring, if that were the problem, I would think would cause a code of some sort. Unless it's only a problem that the reluctor ring is plugged up that only bothers at low rpm.

The problem I am assuming was before I replaced the front brakes. I did a road test and looked at the pads and rotors a few days before i replaced the front brakes. They complained about "a noise" which I never heard. Or at least i don't remember hearing the pump running on that road test. But now it's doing it. I did explain to them what the noise is (they're not very mechanically inclined. Also not sensitive to the fact that it's a lot more effort to do this crap in the middle of winter, they just don't get ithat I guess. I tried getting them to have me do this work around Christmas when we were still in "Global Warming mode" up here).

The rear brakes are drums.

I don't really feel anything abnormal as far as pulling one side or the other, either before the pump runs or on the stops I do where the pump isn't running, feels fine. I am not concerned about the safety aspect at all, this seems like just an annoyance.
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post #6 of 7 (permalink) Old 01-21-2012, 07:19 PM
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This is common to just about any GM vehicle its called sensor drop out. As the wheel speed comes almost to a stop a sensor will drop out and give the ABS computer a false lockup. I am a technician and this is almost a daily thing. I've had good luck by going for a drive with the scan tool attached with all 4 sensors in a graph start recording and drive around the block. If you feel the ABS kick on you will see one of the graphs fall to zero thats your sensor that will need to be replaced. Its built into the hub so they do cost a bit to replace.
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post #7 of 7 (permalink) Old 01-24-2012, 08:43 PM Thread Starter
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Thanks, will keep it in mind. I was also reading something about the reluctor rings like to crack, they are out on the end of the CV joint? I guess will cause a problem. I wonder, since i am not a tech anymore, if I took it to autozone if they'd let me do that road test with their scanner? I know you probably don't know, but thinking out loud.
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