jdugan

Hey guys I have a 2000 silveado 4wd 5.3. I just had a abs sensor replaced that was recalled by chevrolet. Now before they replaced it every once in a while my brake would pulsate while I was driving forward and only when it was under 10mph. Now every time i get under 10mph the brakes pulsate. As far as i can tell all of the pulsating is coming from the front two brakes. I replaced the pads 15,000 miles ago so they are in like-new condition. Maybe the rotors are the problem??? but why would it pulsate then and why when i am only going less than 10mph??? There is no scraping sound just a terrible pulsating. When the truck is stopping from 10mph - 0mph is takes about 30feet. Any ideas when the problem could be???

Sonny01

Take it back to the dealer and have the voltage of the ABS sensors checked...they have to jack the front end up, unplug the each sensor and connect it to a volt meter and then spin the tire by hand. The sensor could be good but the hub could be so rusted up as to more the sensor away from the ring inside the hub. This makes the voltage lower and at low speed the ABS computer thinks the wheel is locking up and commands the ABS system on. This is a common problem with these trucks. Sometimes you can remove the sensor and clean the hub...don't let rust get into the hole...the best thing to do is replace the hub itself if you have low voltage. If you have a lower voltage on one side take the good sensor and put it on the bad side...if it's still bad it's the hub...if it's good then it was the first sensor. You can actually check this yourself if you have a volt meter. If I remember correctly 350milli volts is the minimum.

Sonny01

I found my previous post:
If your sensors are reporting different voltages then the ABS thinks the low voltage wheel is locked up and activates the ABS system.
Here is the sensor test:
Jack up front end...remove a tire...Disconnect the sensor from the wire...plug an AC volt meter into the sensor line...reinstall the tire and give it a spin while watching the meter. Anything under 350millivolts is bad and you either need a new sensor or the rust has moved the sensor so far away from the ring inside the hub it can't get a good hit as it moves past it. Do the other side...if you get a good reading put that sensor on the bad side and spin it again. If the voltage is up then the original sensor is bad. If the good sensor is now bad you need a new hub or more rust removal...get a new hub.
I just found it...02-05-25-006A ABS Activation at Low Speeds (11/26/02). This is the Tech Bulletin from GM that tells all about the ABS problem.
Also...this trucks had a recall about their ABS sensors...I got a new sensor on one side and GM paid for a hub I replaced on the other. Check with a dealer to see if your truck has the recall.
Sonny01

jdugan

I think that both of you guys are exactly right... there is a recall on my vehicle for the abs sensor and the front hub/bearing assembly. The recall is # 05068. The messed up thing is that the day of this post i had just gotten out of the dealership who claimed that they replaced the abs sensor and that it fixed the recall. ...as soon as i drove off the lot the problem became really bad! So what would that point to... a shoddy job by the mechanic??? I have to go in and see them tomorrow and this specific problem is a little over my head, so any help that I can back up my case with would be greatly appreciated!!!

jdugan

hahaha just realized you made both posts sonny... thank for the help.

ps. i'm and idiot.

Sonny01

Just refer to this Tech Bulletin and you should be OK:
02-05-25-006A ABS Activation at Low Speeds (11/26/02)

geneb11

I have been having this same problem.If you guy's remember I posted about this a while ago. once in a while my brakes would pulsate at low speeds just before stopping,but it went away. Later a thought I had a bad right hub,but turned out to be a bad rotor. I replaced my Right front hub and and the pusating started a over again. When I came to 8 MPH forward and reverse the brakes would start pulsating. I sent an e-mail to the where I purchased the hub and they told me they recommend selling in pairs,so I bought another one for the drivers side and thought that would be it. Wrong,it still pulsates I had to pull the fuse to make it stop. One of the sensors was damaged in shipping so I used the old one, so now I have two brand new hubs and one new sensor and it still pulsates. What is causing this. Does the truck have to be put on a computer? Maybe I should buy a new sensor and see if thats it. I probably should bring it in for the recall.

__________________
2000 Chevy Silverado LS
3dr 4x4 5.3 Vortec

Sonny01

Do this before you spend any money:
Jack up front end...remove a tire...Disconnect the sensor from the wire...plug an AC volt meter into the sensor line...reinstall the tire and give it a spin while watching the meter. Anything under 350millivolts is bad and you either need a new sensor or the rust has moved the sensor so far away from the ring inside the hub it can't get a good hit as it moves past it. Do the other side...if you get a good reading put that sensor on the bad side and spin it again. If the voltage is up then the original sensor is bad. If the good sensor is now bad you need a new hub or more rust removal...get a new hub.

wafrederick

The dealer cleans the sensors and that is the fix for the recall.You are better off replacing the wheel bearing and thye do have problems with the wheel bearings.I have heard to stay away from an AC delco wheel bearing,nothing but problems.