It use to work before I had all complete gasket set and head resurface, pressure tested, and valve job, done. I install it myself everything seems to be working except for my 4WD. The transfer-case is not broken i never mistreated, It's not push button (4x4), thinking back my friend was placing the battery back when he mistakenly touch the positive and negative together with a wrench he was using to tighten the terminals, it made a huge spark while they were both connected, could it fry a relay or something I don't know if there such a thing to activate the 4WD Additional information: there is some kind a sensor sticking out what seems to be connecting to the front behind my skid-plate (attach to the front part of the transfer case) there is a wire connector; I am stumped......