I have a 2001 powerstroke that I built the transmission in. It worked correctly for 6 months. Now suddenly the tcc won't disengage. Can't even put it in gear, forward or reverse. I know the common causes, low fluid, poor filter installation, bad tcc solenoid, low oil pressure and torque converter. but I unplugged the harness and it goes into gear just fine. So it's gotta be in the wiring or is being commanded to lock up. I had some computer troubles in the past months and replaced it . Any ideas. I'm kinda stuck.

 

My idea would be to electrically check the circuit to the solenoid for a short to ground.

 

I removed the #4 purple/yellow wire at the trans. It is the ground for the tcc solenoid. Plugged the connector to the trans and when I put it in reverse or drive , it just dies. Converter is locked up tight. When I in plug the connector, ,it goes into gear just fine . Any suggestions? Sounds like the solenoid pack itself is shorted to ground internally. And by unplugging the connector I am removing the power to the tcc, not just the ground. As there is no wiring in the trans. I have yet to pull the pan. These are just theory's of mine........I'm stumped!