I understand the IAT sensor can cause hard shifting problems. I'm trying to check mine out. I have 5 volts going to the sensor with the key on and the sensor reads 1.3 ohms between its terminals. My engine light is on but I don't know the code.
Anyone know the specs. of the sensor?

See the chart at http://cid-54465800aad91b49.office.live.com/self.aspx/pub/88254g69L.gif. The IAT sensor works the same way as the ECT sensor. You may want to do a search on this forum. I even posted a couple of times on them.

I suggest you get the codes read out first and then go where they take you. It's hard enough to troubleshoot based on the DTCs. Guessing and throwing parts at the problem will usually waste time and money.

As far as the control circuit for the transaxle, see http://cid-54465800aad91b49.office.live.com/self.aspx/pub/va151769.pdf. You can see that the PCM is in the middle of it. Good luck.