[rcurley1]

ABS

Moderator you were right :thx just replace the hubs and save time and $$$. Had tried a couple sets of sensors and they just weren't reporting right and driving me and the ABS carzy. Just incase anybody else wants to know the sensors wind up connecting under the car drivers seat right by the air pump.

 

[imgntht]

Anyone know the part number for the ABS sensor by itself? I have Duralast hubs with only 15K on them replaced in March 2013. Thinking of trying to test the sensor first.

 

[imgntht]

Still haven't fixed my low wheel speed braking issue as it is now happening so infrequently, but still happening. Plus it has been closed as heck here in Chicago. Is it possible to simply replace the wheel speed sensors rather than the entire hub? I see them for sale, but not sure if there are different hookups.

Also my ABS light only comes on when I first start the car. By the time I reverse out of my driveway and then put it in drive in the street, the light goes out within seconds of driving forward. Does this help to diagnose anything from other's experiences? Wet weather seems to bring this out a bit more too, but it may just be my imagination. I can go days/weeks with no issue at all, then all of a sudden I may get the pedal pulse and odd straining noise. When I first start the car on cold mornings I get the straining noise VERY loud. I'm worried it may be the ABS module itself as it sounds like it is trying to do the ABS initialization check like the newer Acadias have at like 20mph.

Thoughts?

 

[The Moderator]

To verify the correct part number for any part on your GM vehicle, go to the following website:

http://www.gmpartsgiant.com/Page_Product/CheckPart.aspx

 

[Mrtechhead]

Hmmm!

Your pulsing issue sure sounds like the same thing I had, which was resolved by cleaning the rust from under the ABS sensors. The ABS light issue doesn't jive with the symptoms I had. My light never came on. Still, given the relative ease of checking the sensors I'd go there first before tearing into the rest of the system.
However, your hubs are relatively new, so it's not likely, although not impossible, that the sensor spacing has been thrown off so soon. Many people have mentioned that the only hubs worth buying are the Timkens due to quality issues with some of the other brands, including ABS issues.

BTW, last fall my left wheel bearing went out (120k miles) so I ended up replacing the hub anyway. Upon the recommendation of my mechanic friend I ordered Timken and upon the recommendation of folks here on Trailvoy I got them from Rock Auto for only slightly more than the discount brands.

Best of luck.
p.s What part of town/suburbs?

 

[imgntht]

Just took off the ground that is under the drivers door and cleaned off all the rust. Light still came on when I started it up. I haven't driven it yet as I also replaced water pump and fan clutch this afternoon. (next up a trans leak at the oil cooler line...ugh).

I'm in La Grange Park, so not far from you in Berwyn. :thumbsup:

 

[jimmmmay]

replaced hub with sensor, still not working right?

Hello, I have a 2002 envoy xl and have the same low speed abs issue. I replaced the hub but with a cheap china made assembly and the sensor seemed to clip in real good, didn't really bother to look for rust in the wiring connector on the car side, but i still have the same issue? Could I have a bad hub assembly with bad sensor or is it possible the connection from the truck side is rusty? I am about to order a better hub and do this all over again unless someone has any ideas?

 

[Bucko]

Rear wheel ABS sensors

Hi, I was testing the front sensors and they are OK, but when I tried to find the rear sensors I could not locate any wiring from the rear wheels for them. Can you educate me on their location and wiring route?
I know there is a problem in the rear because I tested the ABS by braking hard in a wet parking lot and the rear tires locked up. The fronts did not.
Thanks,
Philip

There is no bearing hub assembly on the rear axle as the race and bearing are on the axle and in the axle housing. As replacing rear bearings is truly a major undertaking and not normally associated with abs problems, that is not even a consideration.

However, the rear does have an abs sensor which is not normally associated with abs problems caused by bearing wear. One problem mentioned by others is corrosion causing interference with electrical connectivity which may be more prevalent in areas where highways are salted due to icy conditions.

That said, the most likely source is at the front hubs where I suggest you start by process of elimination.

And again I suggest a $20 Chilton's Manual from your local auto parts supplier which will save you time and avoid further delay and far greater expense in the event of a vehicle breakdown at the time and place of the vehicle's choosing.

 

[mcewans]

My Experience

So I had the same issue with my ABS activating at low speeds. I saw the writeup at it stated that you need to have at least 450mv with the wheel spinning at 1 rev/sec. I don't know if this make a difference, but I used a Fluke DVM that measures true RMS for the AC signal. When I started out, I removed the calipers, pads and rotors on each side and disconnected the ABS sensor from the connector and hooked up the DVM. I did check the resistance of each senor and I was getting around 1050 ohms on each side. For whatever its worth these are AC DELCO parts. At first I was getting a signal of around 60-80mv on each sensor. After removing the shim on each hub and cleaning the rust off the opening, the signal went up to 100-150mv at 1 rev/sec and around 280-300mv with me rotating the wheel as fast as I could. I even checked the signal at very low rotation for spikes and I was getting around 28-30mv from just barely turning the wheel. More important was that the signal was consistent on each wheel. I don't know where the 450mv signal threshold was obtained or what kind of AC signal it is referencing to whether its peak to peak or RMS. I know if you use a "cheap" DVM VS a Fluke with RMS, I am guessing that you will get a different reading. I know that there is a similar issue with the ABS sesnsors on the older Chevy Silverados and that threshold was 350mv. I am curious how these readings were determined, because my meter is reading much lower readings, but the ABS activation on low speeds is no longer an issue on my Trailblazer anymore.

 

[JoJoChevy]

Changed the sensor but light is still on.

I changed my driver side abs sensor because O'Reilley's told me it was bad after the diagnostics. But now it is worse. Is it ok to clean the ring with the pick up rings (that is read by the sensor)? it is pretty dirty in there. If so what can I clean it with?

 

[EnvoyBoy2004]

You can use a brake cleaner aerosol spray. Also check the surface where the sensor mounts, if there is rust or corrosion build up, the sensor will not output a good signal.

 

[ryanmattison]

thanks

I've been having the same issue with my 02 TB lt, I'll have to give this a whirl when it warms up a bit outside. similar issue on my wife's 04 venture awd which disables the abs and awd systems, maybe a good cleaning is all those sensors need as the bearings themselves seem fine.

 

[tokanero]

hey guys,

WHERE CAN I BUY SHIMS??

im having this issue on my silverado and my familys tahoe.... cleaned up the hub etc, but the new sensors i bought stick in .73" when the old ones stuck in .67"

if i were to install these and run the truck, the reluctor would catch the sensor and break it... if i had shims id be all set i believe

That is a heck of a good question....I went to my local pick your part salvage yard and got a handful of different thickness shims off several vehicles. This can be a pain if you're not into doing this because you have to remove the tire and the brake caliper bracket.