I'm having a new problem with my 4wd that I can't figure out.

When I turn the switch from 2h to 4h nothing happens, no clicking, no lights, no nothing. I've tried the following.

I just replaced the Transfer Case Shift Motor.

Checked the switch. It gives me 360 ohms on one position, 1.1k on the second, and 3.3k on the last. (I don't remember the exact resistance readings, but they're right.

With the key on, I see 5 volts to ground from one of the blue wires at the switch.

I've checked all the fuses that had anything to do with the 4wd or the gem, they're all fine.

I took the battery off to "reset" the gem, didn't do anything for me.

Is there anything else I can do before I shell out $120 for a new gem?
Is there a wiring diagram floating around somewhere that I can look at?

Thanks for your help.

 

Quick search of this forum brought up a few threads on similar topics

https://www.f150online.com/forums/el...-problems.html

https://www.f150online.com/forums/el...ipers-etc.html

https://www.f150online.com/forums/el...-engaging.html

https://www.f150online.com/forums/el...-location.html

Not always electrical, could be mechanical stopping it from shifting into 4H or 4L

 

I've already read through all those and none of them really solved my problem. What would really be helpful is a wiring diagram of the 4wd system. There doesn't seem to be one in my hayes manual that I can use to troubleshoot.

I forgot to mention, I'm not having problems with anything else controlled by the Gem, windshield wipers, lights, keyless entry, etc.

Where is the Transfer case Relay module located?

 

Which diagrams do you need, ESOF or MSOF ?

 

Esof

 

The 1st 4 picture in this album are the ESOF diagrams

https://www.f150online.com/forums/me...7-1998-my.html

 

You said you had power at the switch, but is it making it down to the ESOF motor? If you do have power at the motor, will it actuate when you remove it from the Transfer Case? (Indicating a problem inside the TC.)

I've had about every problem you can with the 4 wheel drive system on mine. On the one hand, I can complain that it's not a very robust system. On the other hand, virtually everything is easy to work on / replace and if you do the work yourself, it isn't very expensive. Good luck!

 

My thought was to check the vac solenoid.

mred589 said he already checked that part, so on to the other mechanical items ??

 

Yes I have power at the esof switch, but the power doesn't go directly to the transfer case motor. It runs through the GEM, which in turn fires a relay, which turns the power on to move the motor. My relay isn't switching, and I couldn't check the wiring until I got the wiring schematic. I will check them when I get home.

As I understand it, the transfer case relay fires to turn the selector THEN the vacuum solenoid engages the front axles. Even if the solenoid, relay, or wiring had failed, I would still get a 4wd light on my dash along with a click of the transfer case motor. Neither of which I have.

Thanks for your help
I will let you guys know what I find.

-Ed

 

This is not true.

Until the T-case moves and signals the GEM, the 4x4 indicator will not illuminate.

 

exactly what I meant, I guess I didn't word it well. The 4wd light illuminates once the transfer case is in position; therefore, if I'm not getting a 4wd light that means that I don't have a issue with the vacuum solenoid and it's something between the switch and the transfer case motor.

 

Ok, it looks like my GEM is toast. I traced the motor circuit all the way back to the gem, and the relay is never getting the ground from the GEM no matter what I do.

When I have the motor plugged in the GEM does absolutely nothing. When it's unplugged the GEM will give voltage to the electromagnetic clutch circuit for a couple seconds, but never gives power to the motor. I've tried shorting certain wires to try to trick it into thinking the transfer case was somewhere it wasn't, but that lead nowhere. The GEM never realised where it was.

A little hint to everyone who comes across this, the transfer case motor plug is the same plug that's behind the drivers side kick panel. To test things I just unbolted the motor and plugged it in cab.

So now my question is, where is the best place to get a GEM for a 1997 F150 4wd? Did the GEM ever change, or will one out of a 2003 f150 do the same as one from a 1997?

Thanks a ton for the schematic, it helped a lot.