First thank you for taking the interest in reading my post. Now,
I have a 2004 Chevy Tahoe z71 5.3 engine. and i am getting an error message that is driving me crazy.
I Go to Start the truck and the abs light comes on and 2-3 seconds later the Red Brake light comes on (next to ABS) and the message SERVICE 4WD flashes on the Information center. At this point the Truck wont even Crank. you turn the key and the dashboard shuts down and it does nothing. !!
Doesnt matter how many times u turn the key same thing happens.
what i also notice is that truck is sitting on 2WD even if i just had it on AUTO when i parked it, and if i try to get it to another mode (4WD L or 4WD H or AUTO) it just flashes and it wont change modes, even though i can hear the transfer case motor making noise as if it is moving gears or something.
Now, i leave it alone for a while, an hour or so and i go back to the truck, put my key in and sometimes the message is gone. At this point just turn the key and it starts right up as if nothing has happened. Now i can move in and out of different 4WD modes.
somtimes message gone in one hour some times i have to wait overnight.

First i thought it was a bad starter. had it replaced, just to have it happen again a few days later.
After reading on the internet i found out that when the computer finds a malfuntion with 4WD system it disables vehicle so u cannot start it. Kind of makes sense cause when message gone vehicle starts right up.

My confusion is from reading so many posts. some say is a malfuntion of the Tranfercase motor (moves truck in and out of 4wd), other say position selenoid, others say there is a bulletin from GM regarding the wires that connect to the transfer case. something about it shorting out due to water damage or dirt.

So i attached a Code reader even though there is no Check engine light on it and it returned these codes:
P0740 P0758 P0785 P2761
Now, that was one of those cheap readers and i read i need a better reader to actually read the transfer case codes. Thats my next step, but i was hoping some one had read or encounter similar problem and can maybe point me in right direction.
I should mention when i look under truck there are no leaks. Other than that truck in excellent condition.

Thanks in advance for reading and trying to help...

 

Welcome to the forum. You may want to check for IGN 0 fuse in the left I/P fuse block. That fuse supplies power to the solenoids in the transmission and part of the PCM.

 

Did you ever find out what was wrong??