Good News! (I think). It looks like the problem is not in the ECM. It's one of the switches on the transmission. I think it's the 4th gear switch. There are two connectors on the tranny, one is two wires and the other is a four wire connector, but only three are used. Looking at the Chilton's schematics it looks like the four wire connector is to the 4th gear switch, which means the two wire connector is to the TCC solenoid. When the four wire connector is plugged in, there is a direct short from the "GAUGES" fuse to ground.
Does this fourth gear switch do anything other than drive the "OVERDRIVE" lamp in the indicator lamp panel? Has anyone ever replaced it?
Thanks all,
...Bill