Ok, first thing's first; I am not very mechanically inclined so if I am not very specific or list something crazy forgive me.
I have been poking around the forum and have noted others have had similar problems, so I am sorry to re-post and beat a dead horse here, but it looks like a common enough occurrence, just different problems for different trucks.

Here we go: A few months back I turned my new-to-me Blazer into a submarine. Not the best idea apparently. After it sat in a sandy, watery grave for about 2 1/2 hours, I was towed to a shop. I turned one of my rods into a boomerang and drowning the outside computer, I had a new engine put in (80k miles) and replaced the comp. Since then my 4wd has been causing some trouble. At first the Service 4wd light came on and the 4lo light blinked. I started the truck a few times hitting the 2hi button repeatedly until eventually it switched over to 2hi. The Service light kicked off and all was good.
The next time I tried any 4x4 option, it would blink a few times, the switch lights would cut out, and the Service light would pop on again.
I took it in to get looked at. The mechanic told me he tried a new switch, with no change, and tried a new motor at the transfer case (I'm guessing the guy that makes the 4wd magic happen) with no change. He then put all of my old gear back on and said see a 4wd shop because it was beyond him.
Since then, none of the switch lights work and the Service light comes on after I have driven for 2-3 minutes, but always goes off after the truck is shut off.
Any idea on where to start looking for a problem here? I have checked the fuses (both under hood and under dash) and they are all in working order.A buddy and I pulled the battery and tray and checked the vacuum lines, diaphram, and accuator(?). He said everything was working right in that area. As mentioned earlier, a mechanic tried a new switch and the motor at the transfer case with no luck.
I don't get any clicks, clunks, or other noises indicating that the transfercase is trying to jump into 4hi or 4lo. Basically, I and my pool of mechanically knowledgable pals are stumped.
Before I take it to another shop I was hoping to pick some brains. Hopefully its an easy fix. Any ideas? Anything that can point me in the right direction? Or anything I can fumble around an explanation for to shed some light on my post?
Any help at all would be appreciated. Thanks.

 

The TCCM has stored a code if the service 4wd light has come on. A GM Tech2 (or an equivalent scanner with GM enhanced data capability) must be used to access the TCCM and check for codes.

You can pull the passenger side kick panel off and have a look at the TCCM connections to see if corrosion may be a problem. You should also check the connections at the encoder motor on the transfer case to make sure that there is no corrosion in that plug. Corrosion can cause all kinds of weird things to happen with these 4wd systems.

 

Alright, nowI have something to work with. I'll give the connections a look tonight. If corrosion is present, can I just use a wire brush to scrub them up, or am I screwed at that point? (remember i + car = dumb)

 

It will be fun getting into the connector to get things cleaned. Get some electrical contact cleaner to help in the process. Then to keep it from happening again, use some dielectric grease. Just smear it on the face of the connector, making sure that some pushes up into the receptacle cavities.