2000 Sierra ABS

chris_kucia · June 20, 2014

I'm getting low-speed ABS activation on our 00 Sierra.

Usually, it's just annoying and only increases the stopping distance by a small amount. However, this morning, while backing out the driveway, it activated almost the entire time. I had to practically stand on the pedal to get the truck stopped before rolling into the street.

A few weeks ago, I replaced both front wheel speed sensors with new ACDelco after thoroughly cleaning the mounting surface (plugged the hole first to keep debris out). Didn't make a change.

We went on vacation, so I pulled the ABS fuse for the trip and lived with the warning lights.

In the meantime, I got a code scanner that could read ABS codes. Put the ABS fuse back in and got a bunch of codes, but they were all history so I cleared them all. Most were likely related to the fuse pull - also had one for the right front wheel sensor circuit (C0222?). I have no way of knowing if that was from before or after I replaced the speed sensors.

Anyhow, I've been driving it for a few days since clearing the ABS codes. ABS regularly activates when stopping, plus I had this morning's incident. Not getting any new codes.

Is there a way to diagnose this without going to a dealer? Will I eventually get a code I can work with?

gmtech4 · June 20, 2014

Check the hubs as well ,

A corner garage charges less than a dealer , if they have service information and a scanner they can fix it

You can buy Alldata $27/ yr

chris_kucia · June 20, 2014

Don't know why I missed it in my previous searches, but I found info on the board on checking the voltage of the speed sensors. Can't seem to cut and paste or I'd post an excerpt.

Long story short, rotating that hub about 1x/second you should get 350mV AC across the speed sensor terminals.

txab · June 20, 2014

Check the hubs as well ,

A corner garage charges less than a dealer , if they have service information and a scanner they can fix it

You can buy Alldata $27/ yr

+1

chris_kucia · June 22, 2014

Had to buy a new multimeter - mine wouldn't measure mv.

Anyhow, driver's side speed sensor reads 350mv more or less when I spin the hub at 1 revolution per second.

Passenger side never gets over 200mv even if I spin it faster. So I'm assuming there's a problem with the passenger side.

Going to pull the caliper bracket and disc and clean up the mount point a bit more to see if it makes a difference. Hub doesn't have any play.

chris_kucia · June 23, 2014

Sanded and then filed the hub mounting surface. Couldn't get over 250mv on the passenger side.

So I grabbed the old sensor from the driver side and replaced the new Delco sensor. Got similar readings to the new driver side sensor.

Put it back together and the problem is gone.

So it looks like I replaced one bad old sensor with a bad new sensor. But at least it's fixed.

absinthminded · June 28, 2014

Cool, I just got done completing a bunch of work to the front end of my 03 Sierra and now I am getting the same issue. ABS as I slow to a stop. I'm not very handy with a multi meter...guess its time to learn. I'm going to start by cleaning the sensor and the surface around the hole where it mounts?

chris_kucia · June 28, 2014

If I had to do it all over again, I'd start with the multimeter first.

No point spending time cleaning up the sensor that's already working fine. With the multimeter, you can figure out which one is the problem.

What I did was jack up the front end and pull the front tires. I put one lug nut back on to hold the brake disk in place and disconnected the abs connector. I used a couple of small alligator clips on the leads in the connector and put the multimeter on those.

Then I took a big ratchet and socket and put it on that one lug nut and that let me have pretty good control rotating the hub assembly at the one rotation per second.

Then once you figure out which is the bad one, then you can pull the caliper and the disk so you can get at the sensor.

absinthminded · July 9, 2014

Thanks a lot man. do you have the part number for that sensor? I kept the old sensors from my old hubs when I swapped them out. Id like to maybe try one of those.