Brakes- losing antilock feature

[chessy56]

As I'm driving along, the ABS and Parking Brake indicators both light up on the dash. They'll reset after shutting off/restarting the engine. I've experienced the ABS system activating as I'm pulling out of my driveway and I apply the brake when I reach the apron of the driveway. The condition is intermittent but is occurring more frequently. Is it possible that I'm not sending a pulse back to the brake controller from one of the hub assemblies?

About 150K miles ago, I replaced the left side hub up front (felt bearing wear). The right side is still stock after 315K miles. If I had to guess, I'd be focusing on the right front hub assembly. What might the rest of you think? Any quick/dirty/CHEAP way of diagnosing this condition?

[DmaxMaverick]

That's a LOT of miles on the bearings. They don't usually last that long. When they go, they ABS will normally have issues. Even if they "feel" OK, jack the wheel off the ground and give it a push/pull at the top/bottom. Any bearing movement indicates a failed bearing, and the likely cause of the ABS issue. Otherwise, the sensor in the hub is probably corroded. The solution for either is the same.... Replace the hub.

[DieselDavy]

Hi Chessy56,
I'm thinking along the same line as DMax.
Better check for bearing play. I'll bet it is time for both of them.
When mine got a little play in them I almost ran into my own retail store breaking off a iron hand rail before getting stopped. Antilock brakes kicked in, peddle went to the floor and only my e-brake saved my bacon!
Change them before this happens to you!
(BTW, I had no lights before or after this event but your experience in your own driveway is a big indicator, I think....)

[chessy56]

I guess it would be prudent to change out both (preferably) or at a minimum, the right side. Whenever I rotate my tires (every 8K), I always grab the tire top/bottom and give it a shake as well as from the sides (feeling for tie rod wear). So far, I'm not feeling any, but it's probably worth changing them out. Easy enough to do. I do know the slide pins on my calipers are worn- both sides. They need swapping out too. (And the hoses, probably a section of steel brake line, the master cylinder.....)

[chessy56]

OK, so I replaced the upper & lower ball joints (they were toast) and the bearing hubs on both sides. For the first few hundred miles, I saw no failure modes indicated- until today. After stopping at a 4-way intersection, my ABS and parking brake indicators both lit up again on the dash.

Any next step ideas? The brake pedal switch? Controller? Harness?

[More Power]

The solution for either is the same.... Replace the hub.

I needed to replace one of the front hubs on my daughter's Malibu a year ago. NAPA shoved a replacement across the counter. The box said "Made in China". I cringed.... It looked well made.

Long story short, the ABS sensor didn't work. So, I pulled it, returned it, and bought a genuine GM part. Worked fine....

Jim

[AKMark]

The wiring on the front ABS sensors is crap.

I'm talking about from the sensor plug back to the ABS module. I've had to replace that on several vehicles. The only way to confirm if it is okay is to do an resistance check on each of the two wires (per sensor) back to the module and see if they are good.

Those two wires are twisted because they are sending an Alternating Current signal (much like a generator) and if the wires are not twisted, the signal will not be what it needs to be. So when I replace them, I replace both, twist them the whole length and go.

I have used a few different testers to confirm which sensors are causing ABS failure. The cheap code readers won't do it, but a nicer one can show the readouts from all the ABS sensors and you can monitor it while driving to see which one/ones are causing the issues. Checking resistance does the same thing, except that sometimes you just have a short, and it may only short when the suspension moves with bumps in the road.

Hope this helps, good luck in your troubleshooting.

[wdoc]

My 2001 has been having this for a while, seems worse in summer. Code is C0265 - EBCM Relay Circuit. Common problem it appears. I checked the connections (ground, +12V) and it appears to be the ABS module.
Occasionally I got another code which was related to the wheel sensor.

At 155K miles, the hubs had no play in them but were becoming noisy so I changed them.

The C0265 code is still thrown when it feels like it.
This typically means the relay really is bad and the ABS module should be repaired or replaced.
I use Vehicle Explorer to read the ABS codes because it will read anything in the vehicles.