Updated 15 May--Hoping to get an idea from experts here what is likely happening before I give a garage an open-ended job order to find and fix it.2003 Chev 2500HD 6.0 Gas. For the last while, the ABS lamp comes on sometimes if the back tires (not sure if just one side) go over a bump and also it happens at times during a sharp turn (mostly or always right turns) when the back end swerves. Can be at low speed in a parking lot even.After a while with more driving (it varies how long), for no obvious reason, the lamp goes out until the next time. The bell alarm also happens as for when the ABS lamp comes on, so that works right.I assume something is loose, but what? Thanks.( I know the brakes still work with no ABS, so I am not worried about that )

I have a 2003 Workhorse W22 which is GM. I had that happening after checking all abs sensors and finding nothing wrong I discovered when brake fluid is low ABS and brake warning both come on. After checking brake lines and system I found a brake line fitting on right rear wheel seeping it must have been seeping for 2years master cylinder was low for rear brakes refilled, end of problem. Might be worth checking on yours

Thanks, so that's one possible (will check mine for sure!) Any others?

Moisture can get behind the ABS sensor, and the resulting corrosion will push it out far enough to confuse the system.

I found this, which might help?"Look behind each wheel of the Silverado. On the back of the wheel hub are the wires for the ABS system. The ABS sensor sits on the wheel bearing and hub assembly, and looks like a small rectangular box. Check to make sure all wires are connected and are not damaged."EDIT--nothing like that seen. Do you have to take something off first?EDIT some more-- ok this looks like way too much for me! At least I know what the garage might have to do.https://www.youtube.com/watch?v=OQv5NwCTPRo

A bad wheel bearing can also cause the ABS light. Happened on a friends truck and he brought it to my shop we found that a front wheel bearing was worn out causing the light. It just takes a very slight difference in signal to set the light when going over bumps or turning corners.

ABS Comes and Goes Question-Update | Good Sam Community

cmarq
Explorer
Apr 24, 2019
I have a 2003 Workhorse W22 which is GM. I had that happening after checking all abs sensors and finding nothing wrong I discovered when brake fluid is low ABS and brake warning both come on. After checking brake lines and system I found a brake line fitting on right rear wheel seeping it must have been seeping for 2years master cylinder was low for rear brakes refilled, end of problem. Might be worth checking on yours
BFL13
Explorer II
Apr 24, 2019
Thanks, so that's one possible (will check mine for sure!) Any others?
drsteve
Explorer
Apr 24, 2019
Moisture can get behind the ABS sensor, and the resulting corrosion will push it out far enough to confuse the system.
BFL13
Explorer II
Apr 24, 2019
I found this, which might help?

"Look behind each wheel of the Silverado. On the back of the wheel hub are the wires for the ABS system. The ABS sensor sits on the wheel bearing and hub assembly, and looks like a small rectangular box. Check to make sure all wires are connected and are not damaged."

EDIT--nothing like that seen. Do you have to take something off first?

EDIT some more-- ok this looks like way too much for me! At least I know what the garage might have to do.

https://www.youtube.com/watch?v=OQv5NwCTPRo
wrgrs50s
Explorer
Apr 25, 2019
A bad wheel bearing can also cause the ABS light. Happened on a friends truck and he brought it to my shop we found that a front wheel bearing was worn out causing the light. It just takes a very slight difference in signal to set the light when going over bumps or turning corners.
blofgren
Explorer
Apr 25, 2019
The solder joints in the ABS module on the frame rail are also known to fail causing an intermittent issue like you describe on this era GM. I read all about it while I was watching videos on replacing the brake lines on our new to us 2001 GMC Yukon. The first thing to try before digging into that one is to ensure that the ground wire connection to the frame under the driver's door is clean and making good contact because apparently it can cause it as well.
Campfire_Time
Explorer
Apr 25, 2019
That era of GMs is also known for failed wheel bearings. I'm not sure how the backs are on that truck, but the front is a hub and you cannot change the ABS sensor, you have to change the entire hub. Not real expensive, but a major pain to change as the tend to corrode in the housing and have to pounded out. You may also want to ask this question a forum that's GMT platform specific.
BFL13
Explorer II
Apr 25, 2019
Lots of possibles now. Thanks!

In the video, it looks like the whole front sensor does come out on the 2004 truck. Anyway it shows the wire cord leading away from the wheel so now I know which it is. I hope to poke at that and where it connects up in from each wheel to see if there is a loose connection that affects the ABS lamp. Maybe narrow it down to one wheel to direct the garage to.

Looks like the next brake job would be a good time to get the garage to check for the other ABS possibles. I can't do that kind of garage work myself.
BFL13
Explorer II
Apr 25, 2019
After more Google time, I see this is a common problem with multiple possibles.

Can't find any wires from the back wheels like on the fronts as in the video showing the fronts. Unclear to me if the back ones even have sensors???

This guy with a good report found his problem was in a ground connection or else some other wire connection. He did a bunch of things and can't say which thing he did worked. I will check my grounds (was mentioned in a post above too)

https://www.gmtruckclub.com/forum/threads/2003-suburban-abs-light-issues.96992/
Bubtoofat
Explorer
Apr 26, 2019
The rear wheel speed sensor is located on the transfer case, not the rear wheels. That is if you have a transfer case.

Mike