what is this plug on the transfer case? with pics....

This guys having problems with his 4x system too. Might check it for pointers.
http://www.tacomaworld.com/forum/1st-gen-tacomas/306783-stuck-2h-wont-shift-into-4h-4l-any-more.html

 

i ended up hooking black to black and grey to white, when i turned the key i heard a servo moving in the frint diff and the 4x4 light came on.... after several hours thrashing it in the snow with my son, im certain its fixed, although i didnt see any place for the last random plug to go ....

 

well, that explains the noise... forst time ive encountered anything like this.....