Join Date: Dec 2011
Location: Kingsville, On, Canada eh!
Feedback Score: 0 reviews
You have two relays under the hood on the driver side near the firewall that control the shift motor on the t case, the relays are powered at all times and the gem module gives the ground when shifting in and out of four wheel drive.
If your problem is the same as what I've had happen to me on two different trucks the grounding wire going from the gem module to the relay gets a nick in the insulation and goes green thus no longer conducts.
You can jumper the ground to the relay to test my theory and if the t case shifts you know you've found the problem.
Get the wiring diagram so you know what wire to ground.
The wires that ground the relays are smaller dia than the power wires, I think the one that was bad on mine was a brown wire with a white tracer, there is more than one brown/with white tracer so make shure you have the right one.
Good luck, I spent several hours chasing this problem to find one bad wire.
2002 F350 Lariat crewcab 7.3 SRW 4x4 with 4" lift, stainless 4" turbo back Magnaflow Exhaust, DP Tuner, stock /high Idle/40 tow/80 tow, Glowshift pilar 3 guage pod, trans/boost/egt ,285/75/16 Bridgestone Dueller Revo 2's(best tire ever made!) and over 260000 miles on it and still running