ABS low speed activation

[jjaaam]

Sorry if this is a repeat issue but if searched all over the place for a concrete answer with nothing really firm.

Here's my situation - I recently changed all four wheel bearings because some were making noises and were bad (2007 base model). I just figured at 122,000 I might as well change all of them. Admittedly I used cheaper bearings off of eBay. All was great for a few weeks then I started getting low speed ABS activation. Sometimes the ABS and Traction Control lights came on...sometimes they didn't. Seemed to happen more often later in the day when it is hotter outside.

Took it in for a different issue and asked the mechanic to scan for ABS codes. He said there were three historical codes: two for the right front speed sensor and one for the module itself. He said that based on his experience it was more than likely the module and wanted more $$$$ for diagnosis.

I figured that since the bearings I used were cheap that the right front was the problem. Went to AutoZone and got a new one, and changed it out. Same problem. That started me thinking that the module was indeed the problem.

Went to eBay to one of the vendors that repair ABS modules and explained my situation. He just emailed back and said it sounded more like a speed sensor in the bearing. Since the bearing is new and he's saying it's not the module I'm thinking it might be the wiring...I know that GM sells wiring harness sections for this problem.

Again: symptoms are unintended low speed activation of the ABS. Happens when coming to a stop at very slow speeds. Once it starts happening it will do it a few times then the ABS and Traction Control lights will come on.

What do you all think? Bearing, module, or wiring?

Thanks for all of your help-

[Scottydoggs]

hit a junk yard and get a used ebcm. or ship yours out to one of the sites that repairs them, they test them and send them back if they pass the test.

[jjaaam]

hit a junk yard and get a used ebcm. or ship yours out to one of the sites that repairs them, they test them and send them back if they pass the test.

Was going to do that and the guy I contacted said, based on my description, that it most likely was not the module but a speed sensor problem...

[Scottydoggs]

if you swapped the hub and still got the code for both things, id change the controller. or at least clean its plugs and see if it still acts up.

[jjaaam]

Can these be driven without the ebcm? Also, is there any reprogramming that would need to be done once I get it back?

[Scottydoggs]

it can be driven with it removed. you just have no abs or traction control. no reprogramming needed.

[jjaaam]

Thanks

[markpa]

Check the first 8 inches of the wiring harness after the hub connection towards the engine real good. The wires can co bad there quite often. I just had that issue on my driver side


Sent from my iPhone using Tapatalk

[jjaaam]

Will do.

Wiring on the rear doesn't ever seem to be that much of an issue, does it? More often the front?

[markpa]

Yes. Lots of movement in the control arms and turning.


Sent from my iPhone using Tapatalk

[markpa]

Clean the connection well and dielectric grease it.


Sent from my iPhone using Tapatalk

[Swiggles]

Admittedly I used cheaper bearings off of eBay.

I bet this is your problem. Even the cheap ones from AutoZone, I went them once a month. Timken is the way to go! And make sure you torque the axel but to the correct spec or you will have issues.

[Burbman]

Had the same issue. I changed the wiring from about 2" from the hub connector to as far up in the harness as I could get to. Soldered and heat shrink connections. Still had the problem. mentioned to my mechanic and he said the connectors go bad. I ordered this Dorman harness from Rock Auto and fixed the problem. I would do that before you start fooling with the main brain.

FYI, if the module is bad, you can send to Cheap ABS and get it rebuilt for $99. You are only pulling the electronic portion, not the hydraulics, so you can drive the car while the module is out for repair.

[jjaaam]

Had the same issue. I changed the wiring from about 2" from the hub connector to as far up in the harness as I could get to. Soldered and heat shrink connections. Still had the problem. mentioned to my mechanic and he said the connectors go bad. I ordered this Dorman harness from Rock Auto and fixed the problem. I would do that before you start fooling with the main brain.

FYI, if the module is bad, you can send to Cheap ABS and get it rebuilt for $99. You are only pulling the electronic portion, not the hydraulics, so you can drive the car while the module is out for repair.

Just ordered a Dorman harness. Hopefully that's the ticket.

How did you splice into the wiring? Butt splices? Solder?

[Burbman]

Don't use those cheap crimp connectors. Best way is to twist the wires, solder, and cover with heat shrink tubing. Watch this You Tube Video.

If you have to use a crimp connector, cover it with heat shrink tubing if you can. If water gets in the connector and starts the corrosion you will be doing this job again in the spring.

FWIW, I inspected the connector and used di-electric grease when I changed the hub bearing, then again when I replaced the wiring. I never would have suspected the connector, but that turned out to be the problem.

[jjaaam]

Got the harness a few days ago. Spliced it in...so far so good...

[Burbman]

So for $35 you're back in business. This type of symptom is the exact opposite of the main controller not working, it shows that it IS working. The bad connector is interfering with the signal from the speed sensor in the hub bearing, so the controller is seeing garbage data. It's not seeing the same speed as the other wheels so it thinks you're skidding and activates ABS. After some number of events it eventually gets a reading it thinks is out of range, gives up and lights the dash light letting you know it turned itself off. Next time you start the car, the controller does a check to see if all 4 sensors are connected, and so doesn't light the light right away.