Low speed ABS activation

[larry arizona]

I have a 02 Sierra Z71.

 

I am getting a low speed ABS activation. When I am stopping and have light pedal pressure it activates the ABS about 50% of the time.

 

When you apply medium pressure no problem. This can get scary in parking lots.

 

6 months ago I added 285's tires. But the problem just started a couple weeks ago.

 

I thought maybe the ABS is thrown off due to the taller tires.

 

Any ideas? Bad ABS unit?

 

thanks in advance.

 

LA

[GMCSierra04]

Well the larger tires would slow down the reaction of the ABS versus make it over active. I would check to make sure the wheel speed sensors are working along with any other speed sensors that might be on the truck. They can be checked with a DMM, the wheel speed sensors are a hall effect type sensor that produces an AC anaglog signal, each car/truck has different specs on what these readings should be but any Hayne's manual should have specs for your year. Inspect them to see that no teeth are missing or if the air gap is adjustable that its in proper specs. You also could have a faulty pulse motor which could be causing the early ABS engagment. Hope some of this helps.

[budhayes3]

Yea, definitely don't worry about it being the larger tires. When I got my 285's put on, I couldn't be happier at how desensitised the abs became...works like it should now. You very well may have a sensor issue...could be as simple as debris on a sensor or gear giving a false signal. Rust build up will create junk that will affect the sensors also.

[larry arizona]

Thanks for the responses I assume that the sensors are readily accessible with the wheels pulled and would assume that they are at all four wheels.

 

I will look into getting a haynes manual as well.

 

Thanks again.

 

LA

[G-Rott]

Larry,

 

I had the same proble on my "00" 1500 Silverado SC LB 4x4. It was bad front wheel bearing assemblies. 45000 miles and they were both shot. New bearings assemblies and the problem went away.

 

Just a note the bearings went bad on my "new" used "00" 2500 at 60,000 miles.

 

I hope GM fixes the design on those and the window regulators I've replaced 4 between the two trucks and another is going.

[camaronut]

I had the same problem on my 2001 Sierra 4x4.

 

I took it to the dealer that I bought it from, along with the technical service bulletin that explains how to fix the problem, and of course, they couldn't figure it out.

 

What you have to do is to remove both front ABS speed sensors from the hubs, and clean the end-faces off. If you want to (I did), get a small single-edged screwdriver and remove the grease that sits in between the "teeth" of the tone ring, which will make the signal the abs computer reads real clear.

 

So far, everything is back to normal......

 

By the way, the problem is twice as bad when going backwards.....so try to clean as soon as you can.....

 

Good luck.....

[larry arizona]

Turn out bad wheel bearings are the cause. Truck has 45,000 miles on it.

 

 

$1200 to replace at the dealer.

 

Found a set off a wrecked truck with 353 miles on the odometer for $150.

 

Already looking for my next set for the next 45,000 miles.

 

Also looking for some for my Tahoe as well I am sure the bearings on that will also need to be replaced at 45,000 miles

 

No big deal about the ABS sensor going out of cal but the bearing is the bigger worry for me.

 

How many people don't catch this in time and have there wheels fall off at 80mph.

 

Thanks everyone for the help.

 

LA