I finally got the chance to do the check on the OD ground wire. I drove around with the switch installed and every time I went through the gears the transmission failed to shift into OD at 50 mph at light throttle. When I used the switch to ground the OD circuit it immediately shifted to 4th. I then switched it off and it stayed in 4th.
I tried to run the ECT thing to ground and at this point do not believe the PO118 code is valid. From what I can find the engine only has one ECT sensor for the instrument panel gauge which is working fine. The only other sensor seems to be on California engines with EGR system. Anyway the problem must be the PCM or the TPS. I need to figure out how to check the TPS assembly for problems. I checked all the cables and TPS voltage, and kick down cable and all seem to be fine. However when I am at 50 mph in 3rd gear and let off the throttle the transmission shifts to 4th. So for the only way I can make it work normally is to use the switch you had me add. By the way my transmission has the 8 wire plug on the transmission not the three wire connector.