When I activate the 4x4 switch the indicator flashes but fails to engauge 4 wheel drive. According to the OM the continud flash means no engaugement.
Any suggestions?
Thanks,
3 5

Fairly common problem:

http://isuzufaq.ibctech.ca/#faq68

on the front axle there is a sleeve that slides to one side to bridge the split in the axle shafts. sometimes the two shafts are moving to fast or one is moving too fast (if you are drive the car) to allow the sleeve to slide across the splines of the shafts.

you can eliminate the problem by stopping the sleeve from moving at all. keeping it in the locked position.

another method to help it engage, is to push the 4x4 button and move ahead slowly. just creep ahead, sometimes you can actually hear it engage with a sharp click.

if its now working at all pull the cover off and let the engage arm hang down and push the button and see if the arm moves back and forth.