ABS Triggers at slow speeds

[merlin1128]

Heres the story... My Tahoe got hit on the passenger side front pretty good and when i got it back from the body shop they put a new fender, door skin, and remanufactured rim, aligned it... My ABS are triggering at less than 5mph on slow stops... Fast stops no problems at all.... I even had the tires rotated and the alignment checked again and all is pefect....

Today took it to the mechanic because I was due for brakes and told him about the problem with the ABS triggering at less than 5 mph.... It does not do it on every stop, but does it quite often and no lights appear on the dash. He was able to duplicate it and said just like me as you are coming to your complete stop at a slow speed they the ABS trip for a second or so...

He did find a bad wheel bearing hub on the crashed side and the bearing was bad, so that was replaced.... Rotors were shot on the front rusting from the inside out and pitting so new rotors and a complete brake job was done...

This mechanic I go to really knows his stuff and is well known as the problem solver of cars / trucks others cannot figure out... He said they both went over it and the scan tool shows nothing... Front end and everyting is perfect, but when they drove it they did get the ABS to trip numerous times at a slow speed as you ease in to the braking and it does it when you are almost at a complete stop..... He said they checked so many things they don't know what else to check and doesnt want to just start chaning parts in hope of finding out the problem... He is the type that tries to save you some $$$ and is 100% honest, and has known my family for the past 40 years plus...

Anyone have this problem and have any suggestions on what would cause the ABS to trigger on the slow crawling stops right at the very end of the stop???? Moderate to High speeds no triggering what so ever... No dash lights come on.... Scanners show no problems...

Any suggestions????

---------- Post added at 11:10 PM ---------- Previous post was at 11:00 PM ----------

One more thing... He did tell me they drove it around with a scan tool to check wheel speeds and whatever else it does and all showed perfect, despite it still going into the abs trigger at slow speeds at complete stops... He also mentioned they went over everything they could think of and all checked out perfect... But.... The ABS still trigger on occassion at slow speed stops... Not all the time... Sometimes no ABS activation, but then the next stop it could trigger or not trigger... No rhyme or reason or pattern when it triggers...

I do notice that it does it quite a bit on the slow stops when you are turning...

Anyone???

 

[qukon 95]

what yr do u have? go to jnk yrd and get 2 and replace the 2 on the front. but most
likely it's the side that got hit. and u don't have to replace the hub just the sensor.

 

[merlin1128]

It is a 2005....The hub and bearing was shot... It was locking up and did not spin freely... When you say sensor are you talking about the speed sensor? Is it in the hub? I did a lot of searches and am reading that the speed sensor can check out good, but actually be bad....

When I got it back it did exactly what it did before, but now after driving it and going on a trip driving 300 miles it seems like it is getting worse now.... Like whatever is going bad is getting worse...

I am pretty sure I said this in the post about the mechanic that the family has known him a very long time and he is really, really good and gets a lot of problem vehicles other shops cannot figure out to fix.... He said whatever is going bad is showing good still, but will eventually fail and show up on the scan tools he has.....

Like I said I am reading speed sensors can be bad, but show good.... Is it in the hub? Does a new hub come with a speed sensor or is that located somewhere else or does the one that is in the vehicle go back into the hub???? I see they are around 20 bucks on ebay for an AC Delco and for 20 bucks I will roll the dice on changing it....

Can you give me some details on this speed sensor location so I can take a look at it if easy to do or I will have him change it.... Any info you can give me would be greatly appreciated....

 

[alacran]

its the speed sensor. do u have a link?

 

[Sasquatch]

I had the same problem on my yukon and it was the speed sensor.

I have an extended warranty so i let the dealer figure it out, they replaced the hub and that fixed it. Maybe sensor in your new hub is defective?

 

[merlin1128]

The side that had the accident the hub was no good when he did the brakes... The hub did not spin freely and the bearing was no good... Hence he put a brand new hub on it... He did put it on scan tools and I know he said he drove it around and everything checked out perfect...

Now after a driving 600 miles on vacation it is getting worse... I am guessing have him change both speed sensors because maybe the one that came in the new hub could be bad... Like I said I know this mechanic my entire life and my Father has known him since they were kids... I know he knows his stuff and gets a lot of problem cars mechanics/dealers cannot figure out...

The hub was not a cheap one that is for sure too... He knows I am keeping this Tahoe until it goes to the junk yard so he put the very best of everything on....

I am going to take it back to him this week since it is definately getting worse and let him hook his scan tool into it and the one where he drives it and it tells him inforomation that way about wheel rotations and speed...

 

[01HDtahoeNJN]

I have had this problem a bunch of times apparently they get rusty quickly and become faulty (gm dealer mechanic worked on them) had mine fixed three times now they just spray under coat spray on em and it's worked so far..caused an accident in November for me though


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[Centma]

I have exactly this problem with my 2004 Tahoe (in fact, this is what brought me to the forum).

I had a bearing failure in the right front. The dealer said that the ABS sensor was an integral part of the bearing assembly (I had an ABS light at the end phase of the failure; the Tahoe could barely roll then).

Now, some stops trigger ABS. I have been wondering if my left front bearing is nearing failure. With the symptoms reported here, a different cause might be the case: an old sensor on one side and a new sensor on the other. The bearing is expensive, so not on the list to replace just to try.

Edit: I wrote the above waiting at a dealership for a promotional oil change. The guy that drove my Tahoe in/out had the ABS issue happen, so it was on the report when I checked out. In talking with the service advisor, he said the sensors get rusty/corroded (or otherwise a problem). Perhaps when both sensors were the same age/condition, the ABS computer didn't see a difference...but now, with a new sensor (presumably) on one side, it is seeing a rotation difference.

The ABS computer thinks it is doing everything right (so no code or light)...it's a sensor inaccuracy that triggers the ABS if this theory is correct. Anyways, now I have something to go look at...I feared another full front bearing replacement (at $1000 or so installed).

 

[merlin1128]

I know for sure that he had a scan tool hooked up when test driving it and he said they came back with the same readings exactly.... I do see that one being brand new and the other being 6 years old the slightest difference the computer may not pick up and show it as good...

I am going to give him a call in a bit and ask him if he checked out the other side sensor to see if it was rusty or anything like that.... I would say 99.9% sure he checked the other hub because he said he went through everything on the front end, so it must have been good or he would have investigated it further....

Maybe since his scan tool showed everything perfect when test driving it he did not pull the sensor out to check for corrosion on it...

I am sure he will get to the bottom of it and get this corrected and I will post what he did once he gets it all figured out. One thing he did say is in time whatever the problem is that it will get worse and will eventually trip a code or a dash light.....

I don't know if this makes a difference or is related in anyway, but I just went on a trip and my usual mileage was down a few miles per gallon...

I will keep this forum posted.....

 

[Warius3]

I had the same issue with my 2002 Suburban but I managed to fix it myself and here is how I did it:
I tried to clean the tips of the sensors first and that did help alot but did not fix it completely. So what I did next was sanding the small area where the sensor sit on and everything was perfect. if you end up going with the standing trick, make sure you put something in the sensor whole to keep it clean as you sand it. ABS sensors tip needs to be closer to get an accurate reading and removing the rust does the trick.
Very little standing by the way!

Trust me on that...the trick works!

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