2002 Denali Wheel Hub / ABS Question

Ziggs · December 12, 2006

First and foremost, as the admin on another forum, the first thing that I always do when I have a question is search the forum to see if it's already been discussed. I did, and this has, but I still have questions. ;)

Before I purchased my 2002 Denali (a few weeks ago) I test drove it for a weekend and noticed that it had a bad front driver's side wheel bearing. I pointed this out to the dealer and he says he had it replaced. In fact, I drove the Denali to the shop that "did the work" and the dealer picked me up and drove me back to my other car.

That said, I've learned in life that it's hard to trust anyone and that things aren't always what they seem... so I have no idea what, if anything, was really done to the Denali after I dropped it off. They may have just lubed up the bearing to make it be quiet long enough for me to think it was ok, sign the papers, and then it would be my problem.

This morning was the first time that we have had rain since I bought the truck. As I was turning onto a side street and applying light pressure to the brakes, I felt the ABS kick in and pulse the brakes. I thought it was extremely odd for ABS to come on at such a low speed so I made a note to come here and search for any typical ABS issues.

The ABS kicked in a second time when I was pulling into my parking lot at work, on a slight downhill slope, while I had the wheel cut to the left again. By this point I was pretty convinced that something wasn't right with the antilock brakes.

ANYWAY...

After searching the forums here I found quite a few threads dealing with the low-speed ABS recall. One thread in particular mentioned that if the problem is intermittent, then it is probably just a dirty ABS sensor and a thorough cleaning will fix it.

However the same thread also stated that if the ABS is kicking in more frequently, then it's probably a bad wheel bearing causing the hall effect sensor to read inaccurate data.

My question is this:

Supposing that I just had the wheel hub bearing replaced, I am going to pull the wheel off the truck tonight and make sure that I see nice shiny new parts instead of rusty old parts.

If the wheel hub bearing was indeed replaced, would you folks then recommend that I take the truck back to the shop that did the work and ask them to verify that they did not damage the ABS sensor in any way? Or should I just go ahead and pull the sensor myself and clean it up?

I have NOT noticed the ABS kicking in on dry pavement! Only twice now on slightly wet pavement, but at speeds much slower and with far lighter foot pressure on the brake pedal than I would have expected to activate the ABS.

I'd appreciate your thoughts on the issue.

Ziggs · December 15, 2006

UPDATE...

Turns out the passenger side front wheel hub bearing was bad. I had it replaced this morning and the dealer who sold me the truck paid for the parts and labor.

They had replaced the driver side at my request prior to the sale, but apparently their shop didn't bother checking the passenger side. They made it right, though, and I'm very pleased with the way they've taken care of the customer.

GM-Tech · December 15, 2006

Did the new hub have any effect on your abs problem on wet roads?

Ziggs · December 15, 2006

Did the new hub have any effect on your abs problem on wet roads?

<{POST_SNAPBACK}>

No idea. We haven't had wet roads again since.

GM-Tech · December 12, 2006

There's no way they could have just lubed the bearing. It's a sealed unit that would have to be destroyed to try to lube it. They either replaced it or did nothing, but they didn't lube it.

The new hub/bearing assembly, if they did indeed replace it, comes with a new wheel speed sensor, so it seems unlikely that replacement caused a problem in that particular sensor. Pulling the wheel and seeing if the hub assembly is shiny new will tell you if it was replaced. While you have it up in the air, grab the top and bottom of the tire on the side that wasn't replaced and attempt to rock the wheel. There should be no movement. If there is, the hub bearing is on the way out.

Yes, you could have a bad sensor on the other side, another bad hub, or the sensor just needs to be cleaned and reinstalled. It's hard to say if the abs activation is in response to actual slippage of the tire or if it's abnormal activation. It will activate at very low speeds and under the conditions you describe, it could be normal activation. I really can't say for sure.

If you give me your VIN, I can tell you whether or not you have the recall on the wheel speed sensors.

Ziggs · December 12, 2006

I forgot to mention that I have brand new (as in under 300 miles) Bridgestone Dueler A/T Revo tires. I'm doubting that the tires were really slipping on the pavement in either case. Especially given the slow speed at which I was traveling and the light pedal pressure I was giving the brakes.

I will PM you the VIN. Thanks!

Ziggs · December 12, 2006

By way of an update of sorts...

It's still raining here so I decided to get back into the Denali and take it for a short spin around the side streets near my office. I wanted to see if the ABS would activate again under similar circumstances before the drive home in rush-hour traffic.

To be short, it did exactly the same thing.

One of the side streets has a negative 10 degree slope, max. It's not a very steep slope at all. At the bottom of the slope is a stop sign, and water tends to puddle there. I'd guess no deeper than 1/4 of an inch.

As I drove down the slope, I hit my brakes several times without incident. They worked as they should and ABS did not activate.

However once my front tires hit the puddle of water, the ABS kicked in.

This seems to be wayyyyyy too sensitive to me. Granted, ABS is not activating on dry pavement the way that some people have reported it doing when the sensor was acting goofy, but none of my other vehicles would even begin to activate the ABS in such mundane conditions. I'm going to pull the ABS fuse before driving home as I really don't want the computer deciding for me that I should rear-end someone.

Does this sound like the ABS is activating prematurely, or is this normal behavior?

GM-Tech · December 12, 2006

Does this sound like the ABS is activating prematurely, or is this normal behavior?

<{POST_SNAPBACK}>

No way I can answer that.

Ziggs · December 12, 2006

Ok... fair enough. Let me ask one more thing:

If I visually inspect the driver's side bearing assembly and it appears to be new, then it also included a new sensor. Could I then assume that the passenger side bearing assembly and/or passenger sensor is the culprit given the new parts on the driver's side?

I am definitely going to do as you suggested and test the passenger side wheel to see if I can rock it back and forth. I'm just trying to save myself from tearing into the driver's side if it seems highly unlikely that it would be suspect with new parts installed.

GM-Tech · December 12, 2006

It could also be a problem in the rear, though it seems unlikely since it happens when turning. I suspect that if it only does this on wet roads, it's normal. If there's a bad sensor, it would do it at least occasionally on a dry road too.

You don't want to rock it back and forth, but up and down. Back and forth may give you a little movement from the steering linkage.

Ziggs · December 12, 2006

It could also be a problem in the rear, though it seems unlikely since it happens when turning. I suspect that if it only does this on wet roads, it's normal. If there's a bad sensor, it would do it at least occasionally on a dry road too.

You don't want to rock it back and forth, but up and down. Back and forth may give you a little movement from the steering linkage.

<{POST_SNAPBACK}>

Ok... thanks. I'll check on this all tonight as I still want to pull that driver's side wheel off and look to make sure they really replaced that hub bearing.