Ford F150 1997 4.6 pickup with multiple issues.

Hi ppl,
here is the story of a pickup truck i am having problems with. The car from the title came to me with 4x4 not engaging, that was main concern. Concern confirmed and during preliminary check i found other problems like ajar lights staying on, wipers on intermittent mode moves in parts doesn't go full wipe, owner said power windows sometimes inoperative, temp gauge high all the time. Clicking relays behind dash for 10 sec. I diagnosed this as a bad gem and transfer case shift motor.

Scan gave me next dtc:
Gem
B1323, 1352, 1330
P1838, 1867
some codes in pcm and other module can't remeber now.

Using mitchell diagram.
Checks i did and diagnostic process:
I started at the shift motor and shift motor spins just fine with 12V applied directly, the positions sensor in the motor is faulty, there are 4 contacts in this sensor to tell the position, 3 of them are constantly on, 1 is constantly off measuring continuity between yel/wht and them. Shift motor doesn't engage when switch is moved to 4H and 4L (if i put a switch in 4h or 4l during period of those 10 sec of clicking relays i can hear motor running). With plug unplugged at the motor there is no power on motor feed.
I did data stream on gem and there is input from the 4x4 mode switch, brake switch input, transmission range switch is fine and that should be enough to put it in 4x4 but there is no output to the relays and shift motor. So i took out gem completly and applied ground to brn/wht and then to org/lt blu and motor spinned both ways just fine proving that wiring and relays from the gem all the way to the motor are just fine and there is no problem.

With gem unplugged i checked with a test light for power and ground at the connector in fuse box, all is there.

So my conclusion was if there are inputs to gem, power and grounds too but there is no output to motor, wiring good to the motor, with all those other problems it has to be gem, right?? The motor is fine but the sensor is bad and that's why at the start the gem actuates those relays, it sees the motor as engaged and actuates the relays and then after 10 sec as a protection shuts it completly. Those shorted contacts in the position sensor could cause inoperative 4x4 but what is with the other problems? Really bad gem or really multiple separate issues? Any suggestions?
Thank you.

Gems in those vehicles are a common problem! they have a function for windows, wipers, 4x4 and the list goes on.. water normally gets into the dash and ruins it. ive changed my fair share..

I know it is essentially a bcm. How do they go bad? Bad internal relays, shorted components, fried chips, driver problem, memory or program issues? Also does the used replacement unit has to be programmed?
I cracked it open, just a smidge of corosion, all cleaned well.

typically water intrusion is the basis of the issue. they have internal relays that are affected, most of the time its the corrosion that causes "leaking" voltage across the circuit board.. example would be wipers come on randomly, parasitic drain.. so on and so forth!

What about replacement unit? Get a used one? What about programming?

Feedback.
Car is back up and runing.
Position sensor was faulty and i repaired it, contact plate went off from the shaft, i glued it back in a right position and everything is fine.
So there must be some smart strategy inside gem deciding not to send power to the motor with faulty position sensor and with plug unplugged too. A bit weird.
Or maybe because dtcs were stored gem choosed to take the power down?
Valuable lesson learned here which is do not condemn ecu while you are having faulty parts around.