I have a 08 Silverado 3500 flatbed that has the abs and brake lights on, also on the inst screen it has, service brake trailer system, I scanned it and it came up with the c0550 code, but it is a 2 wd. this code relates to the transfer case which I do not have.. This is the only code showing. on the vech. it has the 6.0, automatic, 6 sp, with 134k mi. Thanks for any help

 

On 2wd models, C0550 can be set in the ABS module or the PTO module (if applicable). If you don’t have a factory PTO, the ABS module needs to be the focus.

Because this code specifies an internal fault, it’s pretty straightforward in terms of diagnosis - verify the power and ground feeds are good. If they are, the ABS module needs to be replaced.

You can start by just verifying the ABS fuses (2 of them) under the hood are good. The ABS module grounds on the frame (where the cab bushing mounts) below the driver door. Make sure it’s clean and the wiring is in tact.

If the fuses and grounds check out, disconnect the negative battery cable, unplug the ABS module connecter, then reconnect the battery. Use an incandescent test light (a headlight bulb with a couple of pigtails will work) in series between the power and ground feeds - if it lights, the feeds are good. If it lights dimly (test directly on battery for reference) check voltage at the power feeds with a meter.

There will be 2 large wires (10 or 12 gauge) that are the power and ground for the ABS pump motor only. The power feed for the module is red w/ a black stripe and the ground feed is black. Both are hot at all times so the key doesn’t have to be on.

Additionally, GM has issued bulletins regarding the use of aftermarket devices that hook up to the DLC/OBD port (such as tuners and monitors) that can cause multiple issues. C0550 is not a code specifically noted in the bulletin, but if you’re using one, it would also be worth unhooking it and seeing if that corrects the problem.

 

I just had time to check what you suggested. I removed the ground and sand the frame and clean the wire connection. I checked the two abs fuse's and they were good. I also found a PTO fuse, it was good too. I got under the truck and did not see the plate/cover for the PTO. A new trans was installed just before I bought it and they may have installed one without the PTO. I was having trouble with the wiring harness to the abs module and stoped with it as it was getting late. But after doing this the abs/brake lights are still on. I have not been on the road with it, maybe that is what it needs. Thanks for helping.

 

Hitting the connectors with compressed air will help clean the crud out so you can disconnect them. If you can verify the 2 power and ground feeds are good at the module, replace the ABS module.

 

Ok, thanks very much 👍

 

I just had time to get back with my ABS problem. I replaced the module hoping this would fix t. but no the abs/brake light is still on. I did some research online and found Thai i will have it reprogrammed, does this sound correct, or will it relearn as I drive it. I really don't want to go to the shop with this virus scare going on. Thanks and stay safe

 

Did you verify good power and ground at the ABS module/motor connectors? Is there any part of the harness that looks damaged that could’ve resulted in a short?

Did you install a new or used module? If used, some programming may be necessary if it’s off a different style of truck - 4wd whereas yours is 2wd.

 

Yes I checked all the things you said, it was all good, the module I put on was a new one. I haven't tried to delete the old code but will do it now