i have a 99 f150 ext cab, 5.4, its esof, has a brand new motor on the transfer case, brand new actuator on the front end, when i put the switch in the 4hi or 4lo position, no lights come on, nothing happens, the 4x4 and low range lights work because they come on when you first start the truck up like they should, but when switched to 4x4 it does nothing, what could it be? i also checked all the fuses for 4x4 and they are all good

 

Check the GEM module. It is located under the fuse box and is prone to corrosion.

 

thanks much, is there any definite way to know its bad?

 

Not sure, but if it is corroded, it is a good bet.