I have a 2002 Screw and I used the 4X4 on Thursday worked fine went to put it in on Friday and nothing happened. The light on the dash still lights up when I start the truck but I get nothing when i flip the switch. My first thought was that the switch was bad, but as i messed with it I am able to get the truck into 4X4 when I first start it up it will switch in and engage and the light will light up, but then it will not come back out unless I turn off the truck and start it again switching the switch right after I start it. Also when I start the truck and even if I do not do anything with the 4X4 I can hear what i believe is the solonoid clicking. Didn't know if anyone had ran into any problems like this any advice would be appriciated. Thanks, Travis

 

Getting to far into this gets complicated for board explanation if you are not inclined to far.
It involves electrical modules, switch checks, module triggers to test for outputs, fuses and several points on the transmission, the actuating motor and internally plus the hubs and vacuum actuator.
The first things are the two fuses that are involved. Beyond that it gets quite involved unless there is some luck.
Since it attempts to engage, I would not expect the fuses to the cause.

I looked at the factory diagnostics and can't begin to supply you with all the pinpoint tests to be made.
A tech would look at the situation as how far does it go then begin looking both ways from that point to reduce the time finding the problem.
For example, the dash lamps are lit from the GEM module that has to have the correct feed back conditions to light the lamp and so it goes.
Sorry I can't be of more help than to show how complicated it can get.
Wish you luck.