2002 Villager Transmission Performance

I have a 2002 Villager that runs just fine until you drive it about 50K miles and shut it off. After you restart the first time the transmission shifts when you drive away it shifts hard and the service engine light comes on. The hard shifting continues and on the highway it always feels like it is lagging lit its in the wrong gear. OD on or off does not matter. If you shut it off and restart the OD off light flashes about six times and goes off. If you let it sit for a few hours its fine again intil it hits whatever is causing it. Check engine code points to Throttle Body Positionoing Sensor, which was replaced to no avail. Two dealers currently stumped, any ideas? I'm thinking its something heat related.

UPDATE, The PCM and several sensors have now been replaced to no avail. Any advice or insight appreciated.

UPDATE, It has been determined after several more days of testing (trial and error) and 3 fried PCM's that the powertrain control wiring harness is to blame. Apparently it was somehow damaged and was causing the PCM's to short. I have not gotten the vehicle back yet to confirm that the problem is resolved. They have been wrong before.