Here is what it is, a 01 crew cab F150 lives its life in MI. Not mine but I have been asked to fix it, along with the other many projects I get.
Tcase motor was junk-R&R, inspect wiring all fine.
30A fuse under hood fine, along with wiring no corrosion, owner said it blew 30A fuse last time he tried it, replaced fuse with no results did not even blow fuse.
Relays by battery from what I have read are for front axle, non issue so far I have nothing.
Checked switch has proper ohms and power coming into it
found tcase module Removed checked board appears to have been wet not sure how with its location but these trucks are known to leak.
Key up has no lights for 4hi, 4lo, heck the odometer won't come on right away when you key it up volt gauge, fuel gauge, battery light all dead until it decides it wants to work but truck will fire up.
There is a relay in the dash I know buried and the GEM module plays a role too
Tcase module? F85B-14B194-CA
GEM?
Relays?
Grounds?

Thank you
Curtis

 

First thing I'd do, is check battery voltage, then check it again when running. You may be running on short voltage, if either the battery or the alternator are faulty. Second thing is to see if there are any DTC's. There should be something by now, even if it's a pending code. There may be another module for just the guage cluster ( can't really remember, but there are some years that the cluster has to be changed).

On our '99 ( floor shifted 4 x 4 ), there is a range sensor on the front of the t'case. 2 wires, looks like a oil pressure sending unit ). Ours wouldn't work if that was bad. )

Dave

 

OK, other reason truck was in was grounds power leads, starter battery is new(2weeks old) but was put on charger anyway. The corrosion issues addressed, starter replaced. Made sure charging system was fine. DTC was clear, truck had #6 coil replaced it was dead just dumping fuel oil changed with fuel contamination being I rebuilt this engine 2 years ago I don't want to see it go.
From looking at schematics the module and gem are what runs the show but know this era truck is bad about leaking winshields onto gem modules but being everything else works no parasitic draws. So I'll narrow it down. And the tcase switch not on this one.

Curtis