ESOF either GEM or motor how do I tell?

[tdnp]

I have a 99 f250 with ESOF. I just bought the truck and when I got it it would not go into 4 wheel low. No deal so I bought it. Well, I got it home and replaced the glow plugs. Started it and drove around, tried 4 wheel drive and it would not come out of 4H? So I crawled under and hooked 12 volts to the motor and put it back in 2H(motor works???).

I have checked the switch and it is good. I have 12volts supply at the relays, but no clicking with the switch.

Reason I suspect the GEM
1.) I also have an intermittent problem with the "off" light on the passanger side air bag which flashes 27 on the airbag light.
2.) I have a ABS light?????
3.) Intermittent door ajar.

Does anyone know how/can you test a GEM?

Does any one have a print of the wiring diagram so I can ring out the connections?

I have read that the GEM is either behind the glove box(did not see) or behind the fuse panel(I assume the internal) any know for sure?

Finally, where can i get a GEM reasonable? Preprogrammed would be good.

[JCW]

check out this thread it has some diagrams that might help you.

HELP HERE PLEASE! 24 views and NO ONE KNOWS?

[md18]

GEM is on the left side of the internal fuse panel, dont bother changing parts until you get the codes read out of the gem. Autoenginuity is a great tool for that, or any ford enhanced scan tool capable of reading gem codes. More than likely there will be a code stored that will point you right to the problem.

[JCW]

Where can I buy a good Autoenginuity scan tool?And which one ?

[tdnp]

Well I pulled the GEM tonight just to look for corrosion--none found. I guess that I will have to find someone to read the codes. Thanks for the info