When I switch the dash switch from 2wd to 4wd high or 4wd low nothing happens. All fuses good. Replaced the transfer case motor. Inspected the switch internally-looks good. Inspected the 4x4 control module. Found light corrosion on plug pins and cleaned with alcohol. No other internal damage to module appearant. With a test light it only has power on 1 wire at the switch (which is very low). Power at the transfer case motor is there but, low as well.
Any ideas?

 

Welcome to the forum

Year and engine?

"All fuses good"
Which fuse numbers did you test?

Need year to be specific but pins 1 and 2(C281A) on a 4x4 module should have Battery voltage 24/7, all the time, key on off doesn't matter, orange and dark green wires

Dash 4WD lights will flash if shift motor is not moving
When you turn on the key do the 4WD lights come on and then go off, the bulb test?

 

thanks for the reply. This is a 2002 XLT FX4 4.0 automatic. The switch on the dashboard is totally dead. No flashy thing. As I said I replaced the transfer case motor. Fuses 13 in the power distribution box and 5 in the pax compartment are good. The constant power at the pins on the switch at the dashboard (ignition off), and the transfer case motor plug is weak but there. No other power present on the other pins key on, or truck running (switch to 4wd high or low). Will have to test the pins on the module to be exact but I suspect I will have the same result. With basic power there it has to be something of a signal correct????.

I'm pretty novice at this but, I'm suspecting a fusible link or grounding issue-there is a little rust. Without an exact wiring diagram I'm kind of lost and frustrated so I'm reaching out to you all. It's a nice little truck that I'm hesitant to tear apart electronically. Help

 

There is no power at shift motor, until 4x4 module sends power to it

4x4 module should have power on some wires all the time and others only with key on

2002 4WD setup is fairly simple in that there are really only 3 parts
Switch
4x4 module
Shift motor

Switch rarely has any problem, just 3 resistors in a box
Module has all the electronics and it is usually the part that fails, if no flashing 4WD lights then module will be the problem

Shift motor is just a DC motor like Power window motors, so don't fail often, but unlike power window motor it may only be used once a year, so brushes corrode inside, best practice is to shift into 4hi, 4low then back to 2WD in the driveway once a month, don't have to move the truck just shift it to keep brushes clean, and all gears lubed.
If shift motor has a problem 4x4 module will flash 4WD lights on dash

here is wiring diagram I have for 2002 4WD system

 

Did some more testing on the module. All pins on the module output (gray side) are hot with (gray plug unplugged and black plug plugged in). This includes number 2 which should be the ground???. However when I plug the gray plug into the module-none of the pins are hot so I have to assume that it must be the module. I just wanted to be as sure as possible before I ordered the $200 part. The number 2 pin being hot is intriguing as this might explain some other issues I was having with fuse 10 popping every time I would shift the transmission in to a low gear. Thanks for the help

 

Not sure how you are testing voltage but a "Ground" terminal on an electrical device will show "power", if power is being applied to the device, that is normal.

i.e. if you connect a 12v light bulb to 12v "power" and then test its "Ground" terminal that terminal will show 12v
And light bulb will light up if that terminal is Grounded.

Wrecking yard, OEM and cheaper
2001-2005 Ranger 4WD
2001/2 Explorer and Explorer sport trac 4WD
These used the same modules

 

Got the new module today and it works like a champ. Thanks RonD and forum. I look forward to being a member in the future.
All the best

 

Good Work

Thanks for the update