I had the same problem with my 99 Chevy 4WD, but I just went and bought a new dash push button switch from the dealer insteaded of taking apart the old one. My cost with sales tax was around $45. Easy replacement, just gently pull the plastic dash off (top and left side first) and then I used a long narrow thin bladed screwdriver to gently pry the old switch out and replace. Took less than 30 minutes.
I did take the old switch apart later and found three bad, broken, cold solder joints on the bottom connector pins. I could of fixed, but for the price, just replacing the switch worked for me.
A BIG Thank You to the folks on this NewsGroup for the Help!!!
Yup, the one on the dash is the culpret believe it or not and can cause all
> kinds of wierd anomallies. You can fix it yourself if you have any skills at
> all with a soldering iron. Simply pull the bezel of the dash with your hands
> and remove the switch, pry open the switch and reflow the solder on the back
> side of the circuit board under the plug connection pins(you will see that
> they are cracked making poor connection), I will bet this is your problem, I
> have done a few and solved the problems with the light coming on. Don't
> leave it though as I believe that mine did a half way shift and damaged
> something in the transfer case or differential clutch pack. Also it may be
> something to look into as far as warranty as there has been so many with
> this problem. Good luck
>
>
>
> > My Service 4WD light comes on sometimes and my 4 wheel drive seems to work
> > just fine. I've seen some information that says it might just be a faulty
> > switch. Does anyone know what switch this might be and where it would be
> > located? Thanks.
> >
> >