AWD light on after small drive

I have a 99 Bravada. It acts a little strange. If I put the TCCM fuse in and start the vehicle and go on a snowy hill the AWD will work. This will stay working as many times as I try it. Wheels spinning awd engaged. BUT if I then drive it on normal ground for about 150ft you hear a "click" in the TCCM and the AWD light comes on and will not engage to climb the snowy hill as long as the light is on. If I turn off the ignition and restart the vehicle the TCCM reloads and I can climb the snowy hill, light is off. Until I drive about 150ft on the flat surface again, then the light comes on and the AWD will not engage. I read somewhere that a person had a similar problem and just replaced the TCCM with a used one and it fixed it. Anyone else have this experience ?

I did a little searching and it seems the TCCM sometimes needs reprogramming.

Here's a bunch of reading,

http://www.automotiveforums.com/vbulletin/search.php?searchid=2757765

My tests seemed to show that when the switch was on, I was in AWD.With the switch off, I could do some pretty nice donuts. Kind of fun, as I have never been able to do that in this vehicle before. With the switch on, the service AWD light will come on after a couple hundred feet of forward driving.That's exactly what mine is doing. I have been driving around without the fuse in because of the light. Yesterday I decided to experiment with it in. I found for the first time I have AWD before the "click" in the TCCM and the light comes on . It was great to use it for the first time :) . I might try the switch mod right now. I do have a question about the mod. Biv stated to run one wire to the "hot" side of the fuse box in the ATC slot. Where is the second wire on the switch connected ? Does it go to ground ? Thanks Chris.

My guess is to remove the fuse, use the switch and an inline fuse in series from one fuse slot to the other fuse slot. Make the leads long enough to place the switch in a convenient location.

That's what I figured after I sat and thought it out. Thanks again Chris !

Well, I performed the mod and it is working great ! I did have trouble locating a couple connectors that were small enough to fit in the fuse slots. I used a couple U spades and cut one side off each. They gripped in the slots good. Later on I want to check into the problem that causes the light to come on but for now at least if I need AWD ( I do new construction and get in a lot of driveways that are not plowed ) I have it by flicking the toggle switch. Thanks again.

Good work, thanks for the update.