nkeen07

Hi everyone. Looking for some help with my 07 NBS Silverado 1500 LTZ. I don't drive the truck daily, and recently when I started it up after sitting for about 3 weeks the ABS light stayed on, followed after about 10 seconds by the brake light. I drove it for a day and it the lights were still on, but the next day while driving they went away and stayed off until I parked it (didn't come back on). Well, today after returning from a trip I decided to see if they were still off. To my displeasure they were back. Since it was wet out, I decided to try a few things:

1. Put it in auto 4wd and see if it functioned properly. To my surprise it functioned properly. Assuming that all wheel speed sensors drive this functionality, I am thinking that a speed sensor is likely not the cause.
2. Checked front hub tightness to see if bearings seemed worn, just in case a speed sensor could still be the cause - hubs were solid
3. Slammed on brakes when noone was around in the pouring down rain, and I did indeed go into a full 4 wheel slide with no ABS functionality, meaning it's not a false light.
4. Checked fluid height - was between max and min, so I added just a bit to see if that could be causing an issue (unlikely I know), but no change.
5. Pulled ABS fuse - Was good and contacts were clean, but roughed them up a bit to be sure.
6. Crawled underneath truck and checked the large connector and wires going into the module forward of the fuel tank. Didn't see any concerns. Back in the day (4 years ago) I had a squirrel demolish a few wires near this connector and I had re-wired them, but everything still looked good and water tight. The syptoms when this wiring got messed up were very different (extremely rough shifting and non-functioning 4wd with CEL and ABS light on), so I doubted this was related, but checked anyways.
7. Since I don't have an OBD scanner, I ran to Advance Auto with hopes that they somehow had ability to reach chassis codes, but they did not, so I don't know what codes I'm throwing to search this.

So, I started doing some research, and I'm not finding anything useful on this issue for NBS trucks. I have seen a bunch of ~01's which have issues with the ground on the rad cowl (can't find one on my truck), ABS control modules (bad relays), and bad front wheel bearings, but I can't seem to find anyone on the newer trucks that has experienced the same issue. I also noticed that traditionally the symptoms are a little different. It seems that many times these lights come on while driving after hitting bumps or from random vibration, usually pointing to one of these issues; however, when mine first came on the truck had been parked for weeks. When the issue re-occured, the truck was once again parked.

I'm hoping someone has some experience or references they can help with. If not, I'll see if any local mechanics have the ability to read what is going on, and if not I guess I'll suck it up and have the stealership read the codes for me.

Thanks for any help!

nkeen07

I went to the Chevrolet dealer the other day over lunch b/c they were close and could squeeze me in. I was originally told it was free to read the codes, so I said why not. Well, when I got there they said it was free to read them, but if they had to troubleshoot beyond that I would get charged shop rates, but they would check with me first. Well, while I was out looking around on the lot they read the code (supposedly) and it showed a low rear speed sensor voltage (once again supposedly)...but when I questioned the service manager about what sensors it could be he tried to tell me each rear wheel has a speed sensor, when I'm 99.99% sure these trucks just have an output shaft sensor on the transfer case. Anyways, the tech then came in and said that I had a bad wire on the ABS control module harness which was likely causing the low voltage issue (the same wire I repaired 4 years ago due to a squirrel chewing/tearing it out, but haven't had trouble with since), and he said he wouldn't troubleshoot further until I approved him to fix that for $200!!! When I asked how it would be $200 to cut the wire, put 2 weatherproof butt connectors on and be done in 10 minutes he just shrugged. Knowing there was nothing wrong with the wire, I refused the service, and asked him to tape everything back up so I could get back to work. I then asked for the code that was showing and they refused to give it to me. They then proceeded to charge me $55 for troubleshooting fees that I had never approved, but at this point I was just over it (still professional with them, but frustrated that they were trying to pull wool over my eyes).

Gotta love interactions with dealerships. I'll give O'Reilly a shot as someone on another forum recommended they had a better OBD scanner, and if that doesn't work out I'll get to my local mechanic next weekend and have him read the code for me. If that doesn't help, I'll check grounds as others have recommended and go from there. Stinks having to deal with such a silly issue when the truck only has just at 70k miles, but I guess I knew what I was getting into with Chevy electrical issues when I bought the truck in the first place.