I HAVE A 02 FORD SPORT TRAC . MY 4X4 DOES NOT GO ON ALL THE TIME WHEN I TURN MY SWITCH TO HIGH 4WHEEL DRIVE . AND SOME TIMES IT IS IN 4 WHEEL DRIVE AND MY LIGHT DOES NOT STAY ON .
Venture over to www.explorer4x4.com and search for that problem. I have rebuilt several of the motors on the older ones. That is only needed for low, high is just a clutch. Does the light flash? Haven’t looked at my 02 yet.
You have the dash mounted electric (‘on the fly’ shift?
There are a couple of places to check. One is the transfer case control switch. (In the dash)
It should pop out with a small screwdriver.
Do this carefully so as to avoid damage to the switch holder (Plastic?).
Once out, spray with electrical contact cleaner and leave sit for a little while and try the shift again.
I’ve not had any problem with the switches in my '02 Tahoe, but I’ve heard they sometimes need to be replaced.
I’m not sure where your transfer case control module is located but you may want to check it. These are usually replaced when all else fails. (GMs (module) is located left of the instrument cluster behind the headlight switch)
If you need to go further into this you’ll have to check out your transfer case (speed sensors, electric shift motor, etc).
Hope you don’t have to go that far as it will get expensive. Good luck.
Post your final result back here when you find the fault will you? It will be appreciated.
I’m taking this info from a Haynes GM truck/suv 4x4 repair manual.