OK so I've read about 20 transfer case shifting threads on here and still have not identified my issue. It is a 99 F350 diesel automatic. T- case motor is good. Relays are new. All fuses are good. I have no power coming into the dash engagement switch.
Bought this pickup for a backup farm truck and need the 4x4 to work. Help please and thank you in advance!!

 

The power to the dash switch comes from the Generic (or General) Electronic Module (GEM) at regulated 5 Volts, DC. 5 volts won't push through much. The key has to be in the "on" position to have power at the switch. I'm not sure if the negative path for the 5 VDC is grounded to, or isolated from the frame so a test to frame ground might not work....


Here is a link: https://www.ford-trucks.com/forums/9...of-help-2.html You can check out the "related links" at the bottom of the last page, too.


Some early Super Duty windshields had a leakage problem which sometimes caused corrosion on those connections. 5 volts won't push through much...


I suggest checking the connections at the GEM, located above the fuse panel behind the lower dash panel under the steering wheel. Mine were OK on my '01, and I removed the GEM itself and checked for internal corrosion, I had none. but, it seems to be a common enough problem.


There are some really good how-to's on this site that I used. Log in and search "GEM connectors super duty".


The GEM and the connectors are a royal pain to get to, so get as comfortable as you can and take a bucket of patience with you. Take your time replacing the connectors so as not to damage the stabs when you re-assemble them

 

Is the GEM part of the fuse panel? The fuse panel looks unusually clean or new. If that is the case could someone have put a unprogrammed or incorrect GEM in the pickup? All the other functions seem too work ie power windows and such.

 

The GEM is above and behind the fuse panel. I think it is separate, but it may mate to the fuse panel. Somebody else know for sure? I had mine out a year and a half ago, but don't remember that detail.


From what I've seen, the early GEM's (through at least 2001) did not require programming when replaced, but the newer ones did. I'm not sure what year that started. The GEM controls the power windows, door locks, turn signals, lights, etc. so if they are working I'm guessing you probably have the right one. Again this is a bit beyond my experience. I think you can get the serial number from the GEM and take it and the VIN to a dealer to check for compatibility.


There are two connectors on the top of the GEM which are held in place with retaining bolts, one each. I think they take 7mm or maybe a 10mm socket. You will want a short socket and a 1/4" drive ratchet for these guys. The bolts are captive in the connectors. Back them out and then gently rock the connectors out or the GEM. Inspect the stabs for corrosion. Even a little white residue on the stabs can be a bad thing. Clean with a soft cloth and electrical component cleaner. Be careful with the re-assembly. You don't want to bend any of those tabs!


There is a pin-point test for the wires from that connector to the dash 4x4 switch. I think I can look up the pin numbers if the contacts are all clean, but I haven't been there for this problem so that could take some time. I did do it on the pulse lock vacuum solenoid circuit so I know its in my info somewhere...


Hope this helps....

 

OK so removed fuse panel and GEM. All connections look grea . No signs of water or corrosio . Did notice the part number of F81B 14B205 EP and this shows to be the correct one for a 99. But has the date code of 10\11\11 stamped on it... Gonna reassemble and see if anything changed

 

the 4x4 dial switch is filled with 3 resistors, anytime when there is reference voltage involved i would not back probe any wires with a test light...hopefully you used a dvom.
i have seen bad interior fuse junction blocks that causes 4x4 to be inop

 

No I don't like test lights. I always use a voltmeter. But I did get voltage to the switch now!