1997 Ford F-150 4X4 electrical problems

HI, Good Ole Ford 4wd issue, been their many times. Lets start with the basics. 1. In the junction box fuse/relay panel which is under the left side of the dash their is a fuse, fuse number 23 10 amp check that fuse to make sure its good. If the fuse is good you will need to test for voltage at the 4x4 solenoids. The white/light blue is the power wire, so if you have a test light or a voltmeter, make sure you have 12 volts at that connector. Let me know what you find!

Tested fuse in and out of panel. Its good. Solenoids are getting constant 12v they are supposed to but do not receive ground signal from gem when shifted into 4x4 in order to enable them. Haven't bothered to check for a pneumatic leak until I fix the electrical issue.

The best way to test the GEM is to plug in a scan tool and see if you have communication. Looks like the GEM is powered from a fuse that runs through the 4WD high light. I believe you said that the 4WD high light is working? If so you may have a bad GEM module, or a open in the 4x4 solenoid ground wire (red). First I would see if you can get someone to scan the GEM, if not you could maybe try a used module and see if that works. These modules were fairly common in their day. The only thing throwing me off is the GEM is responding to you putting the t-case in 4wd low, ie by grounding the 4wd low light circuit turning the light on. The 4WD indicator switch (on left side of transmission) is in charge of telling the GEM what range of 4wd you want. I think that's the switch you replaced? Besides the t-case clutch relay that's pretty much the whole system. So the two questions, does the 4WD HIGH light come on when you engage 4wd high? 2. Was the "range sensor" you replaced on the side of the transmission?

No 4wd hi light at all aside from flashing on at startup so I know the bulb is good. Yes it was the range sensor that I replaced. I also did a voltage test on the battery saver relay connected to the gem and it came back positive in lower right pin and full ground in upper right pin. This is typically an easy test to see if you have a bad gem. Even a replacement gem of ebay is $150 so I dont really want to spend that for a test. I have an obd2 tester and its not throwing any codes but I dont know if it communicates with the gem or not (autozone tool). I do have a shop I can use that has the $3000 scan tool its just going to be into next week before I can get to it. The 2 wires going from the gem to the position sensor send 5v and 12v. If there was a ground fault wouldnt they ground out? Not understanding how voltage can remain functional with a faulty ground as the sensors job is to ground out the cables depending on what position the transfer case is in.I told you this is a tough one. Im not one to usually ask questions, I can usually google anything but I am stuck on this one and out of ideas.

The final test would be to check continuity on the red wire from the gem to solenoid to make sure you don't have a break in the wire. Disconnect the GEM and the solenoid connector and see what you have. If you have continuity my guess, is a bad GEM. If you have no continuity well you have a break somewhere in that red ground.

Continuity between gem and transfer case position sensor is good. Checking solenoid continuity now.

Both solenoids getting constant power but not receiving ground signal to engage them. Not sure where to find the RPO relay block to test the orange wire. Where is it located. Would much rather replace a relay than the gem.

What am I checking the brown wire for and where on the transfer case is it located(front or rear).