# 2002 2500hd brake question...



## buckhigh (Oct 21, 2008)

When I come to almost a complete stop, my abs is kicking in whether the ground is wet or dry. No dummy lights are coming on the dash. I want to do all 4 brakes before winter. Calipers are only 2 years old. Are the sensors dirty? Bad? Truck has 120k miles so I would rather replace than clean. Are the sensors located on the caliper? 

Thanks for the help!


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## maverjohn (Jul 23, 2008)

The sensors are in the wheel bearing, The bosses truck started doing the same thing and we had to replace both front bearings.


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## buckhigh (Oct 21, 2008)

maverjohn;1510018 said:


> The sensors are in the wheel bearing, The bosses truck started doing the same thing and we had to replace both front bearings.


Thank you!


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## theholycow (Nov 29, 2002)

A complete discussion of it is in this recent thread:
http://www.plowsite.com/showthread.php?t=138976
I posted a detailed howto after having done it just recently.

If your budget is good enough for replacing the bearings, go ahead and do that. Don't get cheap ones. Get AC Delco or Timbren. If not, and if your bearings test good, it may not be entirely necessary but you won't get brand new sensors cheap; gotta grab them at the junkyard unless you catch a good deal at something like discountpartshub.com.


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## buckhigh (Oct 21, 2008)

theholycow;1510045 said:


> A complete discussion of it is in this recent thread:
> http://www.plowsite.com/showthread.php?t=138976
> I posted a detailed howto after having done it just recently.
> 
> If your budget is good enough for replacing the bearings, go ahead and do that. Don't get cheap ones. Get AC Delco or Timbren. If not, and if your bearings test good, it may not be entirely necessary but you won't get brand new sensors cheap; gotta grab them at the junkyard unless you catch a good deal at something like discountpartshub.com.


Thanks for the link. My hub assemblies were replaced 3 years ago, and carry a lifetime warranty (AC Delco). Your link says they come with new sensors? Is it common for sensors to go bad in 3 years?


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## mikes-plow (Feb 26, 2011)

ya major design flaw for gm. if you dont mind the lights on the dash the cheapest fix is to just pull the ABS fuse out. you could go broke changing bearings just to have abs, thats why i said F-it and just pulled the fuse until this set of bearings goes bad. 3 years is about how long mine last as well


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## theholycow (Nov 29, 2002)

It is a common issue. It's just corrosion at the mounting surface (though if you ignore it long enough the sensor gets messed up too). You can help prevent it with common anti-corrosion tactics, I guess. I just left mine covered in a lot of grease, if I have to take it apart and clean it once every couple years, no big deal.

You *don't need to replace the whole hub assembly* if the hub/bearing is working fine and the only issue is a failed sensor. Go to a self-service junkyard and harvest a few ABS sensors; test them before you bother pulling them. I have a spare now so I won't even have to go to the junkyard the next time one goes bad, but I think if I just fix the problem as soon as it happens by cleaning the corrosion then my sensors won't go bad anyway.

Your sensors may be fine. You may just need to clean off the corrosion and they'll work right again.

Pulling the ABS fuse doesn't _only_ cause the light to light up on your dash, it also disables ABS. If you don't like ABS (and don't have state inspections that check for it) then go ahead and do that. Mine can't be disabled if I want to pass inspection, and anyway I prefer letting the computer detect a single wheel turning slower and having it pump the brakes 30 times per second (or whatever) on just that one wheel instead of me pumping all 4 brakes at human speed when I realize that a wheel has been skidding.


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## theholycow (Nov 29, 2002)

A couple more thoughts:

I may be wrong about it braking only the guilty wheel; I know the latest vehicles do but I don't know if my 2002 model does. Either way the computer can detect it sooner and pump the brakes more accurately and a whole lot faster than my foot can.

Since your parts have a warranty, I'd say just try cleaning the corrosion, and if the sensor is bad don't bother harvesting sensors at the junkyard, just get an entire replacement hub/bearing unit. It's not like these last for the life of the vehicle, you'll probably need to replace it again in a year or two anyway.


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## Woodenshoe (Oct 30, 2010)

If I'm not mistaken, pulling the ABS fuse also effects the proportioning valves as well... Your better off unplugging one of the wheel sensors which will automatically disable the ABS system.


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## theholycow (Nov 29, 2002)

Interesting. I thought the non-ABS functions of the proportioning valve were completely mechanical.


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## affekonig (Aug 5, 2008)

This condition is covered in a well-known recall (05068C). Get a hold of a dealer and they should take care of it.


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## Woodenshoe (Oct 30, 2010)

theholycow;1510243 said:


> Interesting. I thought the non-ABS functions of the proportioning valve were completely mechanical.


Dynamic Proportioning...


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## maverjohn (Jul 23, 2008)

Hey theholycow, How do you test the sensor ?


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## brad96z28 (Aug 21, 2005)

maverjohn;1510516 said:


> Hey theholycow, How do you test the sensor ?


Easy and correct way is with a lab scope.


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## theholycow (Nov 29, 2002)

No scope is necessary. Reach behind and unplug sensor from harness near frame/upper control arm. Connect multimeter set to AC millivolt range. Jack that corner and spin the wheel by hand as fast as you can. You should get at least 350mv (I got 1.5v on a brand new sensor). If not, you've found the guilty wheel...first try cleaning the corrosion at the mounting surface and test again, if it fails again then replace.


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## brad96z28 (Aug 21, 2005)

Im sure you can pick up a glitch with a multi meter :laughing: Lots of ways you can test I just recomended the correct one. They also have wheel speed sensor testors but you can not catch a bad wave form with one. Check enough you will know what works best.


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## theholycow (Nov 29, 2002)

The AC 350mv test is direct from the GM TSB, and the GM service manual's normal procedure is similar. Perhaps it may be possible for this sensor to fail in such a way that it provides the correct voltage with a messed up wave form, but this test is sufficient to find out which sensor is at fault for the symptom in question.


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## brad96z28 (Aug 21, 2005)

Trust me there is such a way and happens all the time. Not just wtith wheel speed sensors. Many of the sensors should be tested with a scope. Spikes and bad patterns can not be seen with a multi meter. And it will show a very bad patern with the rust build up.


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## theholycow (Nov 29, 2002)

Ok, so if you fail to identify the guilty wheel with the procedure that GM recommends, you could find yourself a scope to borrow. I've never heard of the GM procedure failing to identify the fault but it's certainly possible. There's no need to go out and buy a scope for this until the normal tests have failed to identify the problem.


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## tuney443 (Jun 25, 2006)

buckhigh;1510000 said:


> When I come to almost a complete stop, my abs is kicking in whether the ground is wet or dry. No dummy lights are coming on the dash. I want to do all 4 brakes before winter. Calipers are only 2 years old. Are the sensors dirty? Bad? Truck has 120k miles so I would rather replace than clean. Are the sensors located on the caliper?
> 
> Thanks for the help!


Holycow is correct.Remove your sensors,clean off the rust with a NEW razor blade on your favorite scraper,use some plumbers crocus cloth or fine sandpaper to get the hub area shiny clean,apply a THIN film of grease to keep future corrosion at bay,clean off plastic,reassemble.Just the extremely slight additional clearance caused by the rust will cause your problem,by eliminating it,you will be back to specs and your issue will be gone.


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## purplehavoc (Jan 1, 2008)

Also check the wires that ground to the drivers side frame mount on the frame. There was an issue with the frames being undercoated, then the wires bolted to the frame and not grounding properly. The bulletin GM issued for this was for "false ABS''' Often happened in wet or snowy weather and usually at slow speeds. GM just had us remove the bolt and clean off the frame and each wire connection, bolt back up and respray undercoat on the area.


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## buckhigh (Oct 21, 2008)

Thanks guys for all the advice. The dealer has the new hubs waiting for me, and warranty will cover the replacement. Typically, for the hubs to be warrantied the dealer has to install them. But there is now way in hell I'm paying them $400 in labor to install these again. I'm just glad they could push the warranty through without them installing the parts. Going to do them myself this time along with all 4 brakes and rotors. 

Have ceramic dura-stops on now, and thinking about going back to semi-metallic?? I don't notice any better stopping power, but do see a lot less brake dust. From your guys experience, is that really the only benefit of ceramics?

Thanks!


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## carkey351 (Oct 18, 2010)

ceramics are the way to go in my opinion. less dust and last way longer than the metallics. they also seem to not tear up the rotors near as bad either. my grandpa put 85,000 on his 2001's duramax brakes -and they were ceramics. Now he didn't snowplow or trailer pull; but still that's not bad I think.


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## 2COR517 (Oct 23, 2008)

Might be worth spending fifty bucks to have it driven on the scan tool. You can clean, scrape, and replace till the cows come home but it wont fix your truck if the abs controller is bad

Semi Metalics are a better brake pad choice for a hard working pickup


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## skostur79 (Oct 20, 2012)

my experience with durastops
ceramic wear twice as fast , but 90% quiet 
tend to run the rotors a bit warmer,

metallics long life half cost , 

just make sure the hardware pins are free on the calipers


ive seen them trucks need harness cleaned every 3 years

not a hard job to grease up when the brakes off,


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## lilweeds (Aug 3, 2007)

Ceramics are OE, stick with em. Most will get 60k + out of them with proper annual maintenance.


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