How To: Service/Replace ABS Wheel Speed Sensor

[Freedom Motorsports]

Originally posted here.

I didn't see this in the Tech section so I thought I would post it up. If I have left anythign out please let everyone know. I have done this on several 1500, 2500 and 3500 GMC and Chevy trucks. I believe that this part of the systems is pretty universal on all chevy gmc trucks.


GM 1500 2500 3500HD ABS Wheel Speed Sensor Service Or Replacement Information Instructions

The compaint most commonly associated with this failure of the wheel speed sensor would be that the ABS system engages at low speed and during normal stopping or pulling into a parking spot.

The problem to be fixed is rust build up between the wheel hub bearing and the wheel speed sensor plug. The build up causes just enough separation between the hub bearing and the wheel speed sensor that the wheel speed sensor loses contact with the hub reluctor ring.

To repair this you need to remove wheel from the hub. Once the wheel is off, remove the brake caliper by loosening the 18mm hex head or torx head bolts at the bottom and top back of the brake caliper. (GM originally designed the brake caliper mounting bolts as torx head bolts, but they were prone to have the head strip out during removal so they redesigned them as hex head bolts)

Sorry about the blurry pics, they are taken with a cell phone.

This shows the bottom bolt.

Once the bolts are out, use a good sized pry bar, screw driver or something you can pry with to pry the brake caliper off of the brake rotor. Be careful not to allow the brake caliper to fall with only the brake line to support them, they have been known to fail after this. Once the brake caliper is loose from the rotor, flip it upside down on the upper control arm and secure it with a bungy cord.

Once this is done you can see the ABS wheel speed sensor on the top of the wheel hub bearing.

Remove the alan bolt that secures the wheel speed sensor and remove the speed sensor from the hub bearing. Plug the hole on top of the hub bearing with something to keep debri from getting into the wheel hub bearing. Then use a heavy wire brush, course sand paper or wire wheel in a grinder or drill to clean the corrosion off ot the top of the wheel hub bearing. You do not want to create a concave hole in the top of the hub bearing, but you want it good and clean.

Once you have cleaned the top of the hub bearing, Paint the cleaned section of the hub bearing with a LIGHT coat of rust preventing paint and allow it to dry for at leasst five minutes.

Then after ensuring that the sensor plug isn't warped or distorted go ahead and reinstall the speed sensor.

Trace the wiring harness for the wheel speed sensor to the plug on the main wiring harness side just above the frame and unplug it from the main harness.

Run the digital volt meter across the terminals on that end of the wheel speed sensor on each side of the truck to determine proper voltage. Once connected to the wheel speed sensor, rotate the wheel hub bearing quickly. You are causing a magnetic signal that generates electiricity through the sensor, so give it a good turn.

When you do that you should have a reading from the volt meter should be at least 350 ACmV's. If the reading is less than 350 ACmV's, remove the wheel speed sensor and replace it. Once it is replaced, retest the voltage of at the sensor to ensure that the issue is fixed. If you still do not read at least 350 ACmV's then repeat the hub cleaning process.

Once replaired and or replaced simplay reassemble the entire wheel and brake assembly in the order in which you disassembled it.

Hope this helps at least a little bit.

 

[gdddup]

nice write up

 

[alacran]

so just to make sure the screw where the the speed senor is needs to be sanded and painted with a little bit of rust protector

 

[Freedom Motorsports]

Not the screw, the top of the hub bearing, to remove the corrosion. Make sure that ir is a "Light" coating of paint, nothing thick at all.

 

[alacran]

Not the screw, the top of the hub bearing, to remove the corrosion. Make sure that ir is a "Light" coating of paint, nothing thick at all.

this i do get, i need to remove the screw and sand down the metal where the screw is placed

 

[A623Z]

Very nice, good free alternative to replacing the hub.

 

[YslasMA]

This thread helped me out a lot, however, you left out a huge step. In order to get to the sensor, you need to remove the rotor as well.

 

[Freedom Motorsports]

This thread helped me out a lot, however, you left out a huge step. In order to get to the sensor, you need to remove the rotor as well.

Sorry, I guess I assumed by the pics that removing the rotor would be a given...

 

[Johnsonmtz]

So to get this straight, it's not an internal issue with the counter ring or the bearings? This is simply just a problem with corrosion between the harness and hub assembly causing poor electrical signal?

My '04 2500HD has had this exact same symptom for 3 years. I always assumed it required a hub replacement and was dreading the $600 parts cost do I just kept putting it off.

What 'anti corrosion paint' do you suggest?

Great write up. It should save a ton of $$$$$

Kj

 

[homerlex]

Thanks for posting this. I'm having this issue. I just pulled the wheel off and found that I have Torx nuts so I need to go get a driver for that.

My question is what dis you use for "rust preventing lubricant"?

Thanks again!

---------- Post added at 11:11 AM ---------- Previous post was at 11:06 AM ----------

... and anyone know what size Torx it is?

 

[Freedom Motorsports]

I am not sure off the top of my head which torx bit it is for the sensor, I believe it may be a T25. As for the issue, in a lot of cases, it is simply a matter of corrosion causing a loss of communication between the sensor and the magnetic gear inside the hub. I personally use Rustoleum brand paint, it is goof for protection against future rust. But don't put a lot, only a light coating, too much and you will recreate the issue with paint instead of rust.

 

[miscrap]

Thanks for the write up! My '05 Tahoe Z71 has started giving me a Traction Active light, along with no power until I get off the gas, when starting from a stop. I also get a groaning noise just before coming to a stop. These things happen once every few days. Does this sound like the issue you're talking about?

After reading the thread, I have a few questions. At first you mention that you use a rust preventing LUBRICANT, then you say PAINT (Rustoleum). At first I was thinking of wiping it with an oil of some kind, now I'm not sure.

Also you said "Plug the hole on top of the hub bearing with something to keep debri from getting into the wheel hub bearing. Then use a heavy wire brush, course sand paper or wire wheel in a grinder or drill to clean the corrosion off ot the top of the wheel hub bearing." So we don't want stuff getting into the wheel hub bearing, but we're using a wire wheel on the wheel hub bearing? I'm confused. Is the wheel hub bearing beneath the hole that we're plugging, or is it the area we're cleaning? Are we plugging the hole from the screw or the sensor? And is the picture with the black rectangle the correct area to clean?

Sorry for all the questions. I was just about ready to order a hub/bearing assembly, but this would be a lot easier and cheaper! Thanks again!

 

[Freedom Motorsports]

Sorry about the lubricant statement, it is paint. But with plugging the hole on the hub bearing before cleaning, you can plug the screw hole if you want to, but the hole that really needs plugged is the sensor hole. You don't want debris falling into the hub bearing and getting on the magnetic gear inside the hub.

It is possible that this could help your issues, but the one thing that I never experienced with it is power loss. At times with some trucks I have seen where you can feel the stability control kick in while moving, but not much of anything from a stop. The groaning noise could be the hub bearing, but if it is then the bearing is probably bad and performing this maintenance will not help. Once the hub bearing has gotten bad enough to "grind" then it is too late and the hub bearing needs to be replaced.

 

[doylee4693]

my truck just had its sensor cleaned for the 3rd time since new,im wondering why not just but an aftermarket sensor?wouldnt it work better then cleaning the faulty gm sensor and getting it again in another year or two?

 

[doylee4693]

BUMP (my abs sensor is going to need help again soon)...any reason why we cant correct the problem by getting an aftermarket sensor?is it built into hub so cant replace just the sensor?

 

[Freedom Motorsports]

I don't think there is an aftermarket option for that sensor. But you can order a new sensor from the dealer without the hub bearing, but if you order a bearing it comes with a new sensor. But to test the sensor itself, you can unplug the harness side of the sensor and test with a meter to be able to tell if the sensor is actually bad, refer to the original post for the ACmV specs.

 

[kashgvd]

Thanks clkelley! This fixed the issue on my Z71. Traction control was activating when accelerating.

 

[ludvball]

I have been having similar problems. It started as traction active coming on and loosing power. Then it progressed to the brakes having the weird stopping. The hub on drivers side was replaced about a year ago, and looked good when looking in the sensor hole. The passenger side hub was bad I have replaced the ABS sensor on driver side, and hub assembly on passenger side, which came with a new sensor.

Initially, everything seemed good, other than the ABS light not going out. I figured it just needed to be reset. About a week after changing the hub assembly and sensors, I am now beginning to experience both issues again. I am thinking the next thing to check would be the ABS module? Any help would be appreciated.

 

[electro]

Initially, everything seemed good, other than the ABS light not going out. I figured it just needed to be reset. About a week after changing the hub assembly and sensors, I am now beginning to experience both issues again. I am thinking the next thing to check would be the ABS module? Any help would be appreciated.

I think that would be the next step.

Can you get your truck scanned? A GM dealer can get the codes of there for you and you will know if its the EHCU (Electro-Hydraulic Control Unit).

I'm going to replace mine asap with a used one for around 250. There close to 500 for a new one here in Ontario. I had a whole bunch of codes and so I cleaned the sensors and now I just have a code which I wrote down and cannot find at the moment but it is a defective EHCU.

Good luck.

 

[ludvball]

Can you get your truck scanned? A GM dealer can get the codes of there for you and you will know if its the EHCU (Electro-Hydraulic Control Unit).

I'm going to replace mine asap with a used one for around 250. There close to 500 for a new one here in Ontario. I had a whole bunch of codes and so I cleaned the sensors and now I just have a code which I wrote down and cannot find at the moment but it is a defective EHCU.

Good luck.

A friend of mine has a cheap scanner that i used before I replaced the hub and sensors. It didn't show any codes. So, I will have to go to my fathers shop and check the codes.

Man $500 for the module.