Service 4WD

I had a windshield replaced today and when I got back in the truck the DIC said "Service 4WD". The 4WD control panel was not lighted and the 4WD was not engaged. By the time I drove 4-5 miles headed to the nearest dealer, the 2WD light lit up and all seemed back to normal. I pulled off of the road onto a back street and tried both 4W High and 4W Low. Everything worked fine. The truck has 95,000 miles on it and I have never had a problem before. My concern is that I am going to tow my 5'er 250 miles back to my home base at the end of next week.

Does anyone have any thoughts here? What caused this? Will it come back? If it returns while I am towing next week, what problems might this cause? The dealer said they are completed over booked until Monday and I have an appointment then for them to look at it if I need to.

I don't expect to need the 4WD during next week's tow, but I don't want to further damage my truck?

Thanks guys.

My first question would be why they needed to put it in 4WD to replace the windshield?

They didn't. Actually they didn't drive it at all. I parked the truck in their service bay and they just replaced the windshield. I only mention the windshield because it was something that was done to the truck. I don't think that had anything to do with the problem.

As I stated, the Service 4WD popped up on the DIC and there were no lights showing on the 4WD control panel. Since then happened and it started working again I have seen no problems. I would like to know what happened, but you can't diagnose something that isn't happening right now. No lights came on on the dash, only the Service 4WD on the DIC.

Earlier models (1999~2003) have/had an occasional issue with the electrical 4x4 system (NOT the auto 4x4). Button cluster (in-dash push buttons) replacement cured the problem in most cases. Some were intermittent and some just quit, but the problem seemed less frequent with later model years. I haven't heard of any later models experiencing this, but that doesn't mean it isn't happening. In every case with the same symptoms when a cluster replacement cured it, there were no adverse effects or loss of use. Only loss of 4x4 engagement (because the buttons were "dead" during the time".

If you are only seeing the "Service 4wd" message and weird lamp activity, it shouldn't be serious. It shouldn't leave you disabled or limping, and shouldn't cause any damage. The best explanation is a mere loss of communication. The 4x4 system is essentially passive, as long as it's mechanically sound. Normally, the worst thing that may happen is 4x4 won't respond to button inputs.

Your problem could be (or have been) a connector or voltage issue, which may intermittent or a one-off experience. If it's only happened once, and everything returned to normal after, I wouldn't lose sleep over it, or spend a bunch of money/time on diagnostics. If it were a serious system issue, you would be seeing the SES lamp and have some stored codes to start diagnostics with. If it returns, the button cluster is inexpensive and very easy to replace. I would suggest replacing it as a first action, before paying the dealer $100/hr to chase ghosts.

DmaxMaverick, Thank you for your input. It has only happened once. No SES light. Just the Service 4WD on the DIC and all buttons on the 4WD module were dead. After 15-20 minutes of driving, and a few bumps on the rough road, it started working and has worked fine since.

I will replace that module if it happens again.

Thanks again. I appreciate it.

Had a "Service 4WD" message in my truck a few years ago. The problem began as an intermittent, till progressing into a continuous over a period of a few months. There was never any problem driving the truck with the message. Replacing the push-button switch panel fixed it. At the time, my wife's Tahoe had a similar problem - that was fixed with a new panel. Like Greg mentioned, I haven't heard of this sort of problem with the newer trucks.

Jim

Thanks for the input Jim. It has only happened that one time. At least I know what may fix it and easy if it starts to happen again. So far only that one time only. Time will tell.