There are also sensors at each front wheel for the ABS, which make it a three circuit system. Any fault in the system will set off the ABS light. Also, the cruise contril is related to problems with these sensors.
The service manual discusses electronics under the hood that control the engagement of the transfer case (motor on the side of the transfer case). Was it the two relays by the drivers side battery that you replaced . They are in a small box 1.5"x3". They are for the shift motor. You can also spray some contact cleaner in the plugs to get any gunk or oxidation out, because it sounds like you may be battling a lot of corrosion issues.
Also if you haven't already, verify power to the 4x4 switch. You say you have checked the fuses, but do you know which one is for the 4x4 circuit? I would replace it just to be sure. If all that checks out, go to the tcase motor and verify power to it. I have heard the motors on the tcase are fairly reliable so it may very well be either a pulled wire or loose connection.
Last edited by bismic; 07-17-2012 at 02:20 AM.