ABS light stays on

The description sounds like a bad circuit from a sensor to the ABS module. To see what the module is seeing will take a scan tool that can read live data and the codes. With the scan tool you can read the speed information from the sensors and see if the signal is getting to the module. There are three sensors in the system, One at each front wheel and one on the transfer case to show the rear wheel speeds. A scan tool can read the data from all 3.
With the code and scan data it would be easy to track the issue.

Thanks Steve. I will try to find someone who has that scan tool. I really have appreciated all your help!

Some part stores have them as loaner tools, but you can get one reasonable as well. You want one that can read the ABS live data as well as engine data. Many will read the ABS codes but not the live data from the speed sensors which is the information you need to see.

It sounds like you may have a wheel speed sensor that is out. These videos will help us find the problem:

https://youtu.be/rTtAnsOlZU4

and

https://youtu.be/Pb6nXV-iamI

and

https://youtu.be/ANWVTh2RQoQ

and

https://www.2carpros.com/articles/abs-warning-light-on-easy-repair-guide

Please run down these guides and report back.

New sensors already installed. That is why I would like him to get a scan tool that can read the live speed data from the sensors. With that you can actually see what the module is seeing. Codes are not going to do much if this is the typical harness issue on those trucks as it shorts out in the harness and shows a bad sensor. The ABS doesn't have very good diagnostics on the 02s so the live data works much better in showing any speed differences from the three sensors it has, unfortunately most of the lower end tools don't show that data, they will only pull codes.
The best solution would be to go to the ABS module and use a scope to look at the actual signal waveforms as that can tell you pretty much everything including if the issue is a bad tone ring because the wave will have flat spots where there should be an AC signal from the sensors. A really neat way to test these is to pull the sensor connector and send a square wave signal through the harness. Then read the speed it shows on the scan tool. Now alter the frequency and you can watch the speed change. If that works, the wiring and module are good but there is an issue with the sensor. Either rust jacking or a bad sensor.

Thanks both Steve and Ken.

Please let us know what you find. We are interested to see what it is.

I may take it back to the garage who put the new sensors in and hope they have a scanner that can assess the ABS system. Worst case scenario I can buy a scanner from Amazon for a bit less than $100.00 which can give me codes to problems for lots of things.

They should have a scan tool that can read the live data, if not find a shop that does. If not I predict that you will likely be told it has to be a bad ABS module as well. Could it be? Yes, but if it's a bad module, why did they replace the sensors? Especially both sensors when they share no connections other than the module?
Unfortunately there are any number of shops that buy a code reader and then fire the parts cannon because "It had a code for XXX and that means replace part YYY" When in reality that is very seldom the case, but they still make money replacing all those parts.

I try to follow a different approach of "test don't guess" So I have the test gear to do those tests. I also generally replace the bad part only. So say the issue on your truck is actually a bad wiring connector in the ABS harness that set a code for a bad RFWss, I'll test the sensor then for the signal at the ABS module if no signal there but a good signal at the sensor, I'll look at the wiring diagram for any connections between those parts. Then disconnect the harness and test there. If there is a good signal there but nothing at the module I know it's in the upper harness. If no signal at that connection it's in the lower harness. Time wise I would take me maybe 20 minutes to do those tests, but now I also know where the problem is and you don't pay for two speed sensors and installation when they were not the problem. But then the shop doesn't get to vacuum out your wallet.

Now how could a DIY person do those tests without any fancy tools? Well let's say that the issue on the code reader says you have a bad Right Front speed sensor. That means the Left side is still okay. So you unplug the opposite side and run jumper wires to cross connect the sensors, so the left side feeds the right side and vice versa. Now go for a drive. If it's a bad sensor you should see a bad left side code now. However if you still have a bad right hand code you know the sensor is good as it's feeding the left side. So now both sensors tested good. Now you look at the wiring and find where those sensors connect to the ABS module. Run those jumper wires from the right hand sensor up to the ABS terminals they feed. Back probe the wires in with a couple of pins and test again. If now the code is gone and no lights you just demonstrated there is a fault in the harness itself and the signal isn't getting to the module.

I am the one who made the decision to replace the sensors hoping that would solve my problem. I always print what you send me out. I sure appreciate you!

Not a problem, I just see a lot of shops that do that. Then they say something like "Well the machine told us that was the problem, not our fault", here's the bill for this next part we changed. In this case there are two ABS systems, depending on if the truck has the optional traction assist or not. Most didn't in those years so the wiring should be correct. The sensors are really nothing but coils of wire and the tone ring going across the face of them generates a sine wave that changes in frequency as speed increases. There were a few issues with them, the most common had a different symptom though, you don't get any lights, instead the ABS would apply as you slowed down and the sensor stopped sending a signal. The ABS then figured that the tire had stopped and it would bleed off pressure in pulses to get it moving again. However the real issue was rust jacking. Rust would form between the sensor and the hub which would push the sensor up out of the hub slightly. That was just enough that the sensor signals would be at different amplitudes and one would suddenly drop out while you were still moving at say 5-10 MPH. The repair is simple. Remove the sensors and clean off the rust, apply some silicone grease and put the sensors back in.

Thanks Steve however that was not the problem. They cleaned everything when putting the new sensors in. I am anxious if the garage that did it has a scanner that will reveal codes as to what is going on.

Yeah, just one of the common issues on them. A scan tool should at least show a code. A good scan tool should show much more. We'll be here in the meantime. Just waiting to see what they find.

Sad to say the scan came up with the code that it was the sensors which both had already been replaced. Don't know what to do next. My Silverado was pulling to the right by the way and I ended up having to have the entire front end replaced.

Do you know the codes? Many had the rust jacking and others were the wiring harnesses that would fail just up past the first connector where the sensors plug in. I assume the rebuild took care of the issue?

Sad to say they ran a scan and no codes came up!

Odd if the light was on it should have codes stored. May have a communication issue in the system. Hard to say without testing.

I have a family member who has a scanner and will try to get him to scan the ABS system to see what he comes up with. He told me the scanner he uses in his work can scan an entire engine.

Hello, I'm Danny.

Just here to add my 2 cents. I would suggest performing a CAN- Controller Area Network scan. This will retrieve all information and codes within all the vehicles systems including the abs system you are having an issue with. Here is a tutorial showing what is involved for performing this scan:

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Hope this helps and thanks for using 2CarPros.

Thanks I ordered one. I saw a scanner on Amazon which was about $100.00 but I will try this one since it was only $35.00. The garage who put the new sensors in once told me the code that came up indicated it was the sensors but later they ran another scan and no codes came up. Sure hope this scanner will tell me what is going on.

Hello again.

Okay, keep us updated as to what you find. Thanks again for using 2CarPros.

Danny-

God Bless 2CarPros as they sure have been helpful every time I reach out to them!

You're welcome!
We're here to help. Let us know what you find after receiving your scanner and check for codes. Thanks again for using 2CarPros.

Danny-

I got my scanner in today but the truck is in the shop getting front end work done and I told them to assess my hubs and replace them if needed. My Son thought that might be my problem. After I get my truck back I will try the scanner even if that solves my problem with the ABS light.

Sounds good.

Keep us updated and we'll go from there. Thanks again for using 2CarPros.

Danny-

Front end done and very expensive! I purchased that Autel AL319 but would not scan my ABS. Called the company and they said since my truck was considered heavy duty (2500HD) that scanner won't work. They recommended the AL529HD. My Daughter told me she has a scanner that would work so I will wait to see if it does scan my ABS. The garage also thought my hubs were in good shape.

Hello again.

Okay, just keep us updated. We're here to help no matter how long it takes. Thanks again for using 2CarPros.

Danny-

I still have not purchased a scanner that will for on my 2002 Silverado 2500HD 6.6 Turbo but now I had all my tires changed and the mileage indicator is now blank! It used to be a challenge to read the mileage but now there is nothing. How is mileage calculated in this truck? Just wondering if putting the new tires on had something to do with the blank mileage now.

The $3.00 scanner does not work on my 2500HD so I may buy one that will work. By the way, do you know how the mileage is recorded for the mileage traveled in this truck? I had new tires put on but now I have no mileage indicator on my dash.

Hello again.

The mileage is recorded from input-speed sensors from the transmission and recorded by the BCM-body control module. The mileage will remain and continue to be recorded but is sounds like you are having and issue with the digital display on on instrument cluster. Do you need replacement instructions for the instrument cluster? Hope this helps and thanks again for using 2CarPros.

Danny-

I will admit for a long time it was not easy to read the mileage. I thought perhaps I could replace a lamp and took the dash apart and lowered the instrument panel but found no lamp I could replace. The light came from a bulb wired into the panel. If I purchase that scanner perhaps it will tell me if the speed sensors are working. If you want you can send me instructions on how to replace the instrument cluster. I would first want to check out the input speed sensors. I really appreciate your help and God Bless you!

As you are getting ABS codes it could point to a bad sensor, however if the speedometer works it isn't the sensor as it uses the same signal. If the odometer display went blank the common problem is a failure of the FET that provides power to the display, or the resistors for the display have cracked free. If you want to see the repairs for that and are good with a soldering iron you can look for a YouTube channel called jeffescortlx he has a number of videos on the GM clusters and does repairs on them as do a few others.
This one covers the odometer issue and other repairs:

https://www.youtube.com/watch?v=TLtDw_Sjh1o

troubleshooting that cluster:

https://www.youtube.com/watch?v=mC1OdwWRFtQ

The garage replaced both sensors but the light stays on and eventually the brake light also. They said they scanned it but no codes came up but I question if their scanner worked on a heavy duty truck like my 2002 Silverado 2500HD 6.6 Turbo. I will purchase a scanner that will work on my truck from Amazon. I hope it will scan the problem with my odometer not showing the mileage. Thanks for the videos sure looks complicated and don't know if I have the ability to do the soldering.

If the display is blank it isn't any sensor. If the sensor went bad it would just stay stuck on a certain mileage or show all zeros. Scan tool won't change that at all. If both the ABS and Brake lights are on that could be any part of the ABS system, a common area for that is the ABS module itself failing. The scan tool issue is because it's a 2500HD, They use a slightly different protocol on the heavy duty version and most of the lower cost tools won't access it, a dealership should have one that will however many regular shops only deal with cars and light duty trucks. There were a bunch of TSBs and service items on those trucks over the years but to know if any apply you would need the proper scan tool for it. My Genisys EVO shows as having the proper software to talk to all the systems on that truck, so that tool might be an option as would many of the equivalent tools like the GM Tech 2, or even a brick (MT2500) if you can get the correct cartridges. The Genisys scan tools are available on the auction site all the time, the newest ones cover up to 2015 but any of them that cover say 2004 or higher would be up to date enough to work with your truck, I wouldn't go back to 2002 as many times they add items as the vehicles age and that may not be in the 2002 software yet it would be in the 04 or higher. They are not the fastest tool out there but they are a solid tool.

I will try the INNOVA 6030P scanner as it is about $100.00 on Amazon. What auction site are you referring to?

Forgot to mention I now have a blank mileage indicator in the dash. I just spent over $2,000.00 having the front end replaced and wonder if the expenses will ever stop!

E-Bay. They have a bunch of them on there both new and used. The blank odometer is not sensor related, it's in the display itself.

The Chevy Garage wants $100.00 to scan my truck and I think I will just let them do it. I do have videos of how to repair that mileage indicator and I may attempt that although I am really nervous to try.

Hello again.

Okay, just keep us updated and let us know if you have any further questions on this issue. Thanks again for using 2CarPros.

Danny-

I have been having help from Steve and Danny. My ABS light stays on even though I had both sensors replaced. My mechanic diagnosed it and it read "error with Solenoid Control Monitor" but I can't find that part on the Internet. He is doing further research for me but sure wanted feed back from you great guys. I also wanted to tell you I lost sight of my odometer. It always was dim but not black. One day I did press on the reset button and it light up. I intend to pull the cluster gauge unit, remove the plastic on the back after unplugging it and look to see if it might be a burn out lamp. Is this a good idea?