E4OD wiring diagram

http://rides.webshots.com/photo/2649993560096577034wsGban

All the power to the transmission is on the red wire. If it shifts at all, that means it has power on that wire.
To test the TCC solenoid electrically, note the position of the RED wire and the PPL/YEL wire in the connector. Then pull the connector and check the resistance between those two terminals. Or, cut the PPL/YEL wire and check the current thru it when the PCM end of the wire is grounded. If you have high resistance or low current, the solenoid or internal wiring might be bad.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Deib</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mark Kovalsky</div><div class="ubbcode-body">
Locking the torque converter in park causes absolutely nothing to happen!

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Cool, that will help. So I was testing it wrong.

There may be hope yet. If the thing tried to lock up, which I hope it does, then I know my problem is someplace else, not in the TC, or solenoids. </div></div>

I wouldn't use the brake method. Too much chance of the brakes slipping if you don't guess enough force on the pedal. Safety stands/blocks of wood are a better bet. Make sure you're not in 4x4.
Then test.

Well, the GV unit changes everything. I didn't see it in your sig. Yes, they will split several signals so you don't really know what is going on.
Good luck on the custom controller.