Okay, I went ahead and pulled the pan, changed the filter and flushed the trans fluid. The replacement transmission is 4 hours away so I figured, what the heck.

So, I test drove it and the AT light is still flashing... My driveway is 1/2 mile long. The AT light is coming on after I drive down the driveway, turn around and get about 2/3 of the way back. I can turn the ignition off, start the truck, and the AT light goes away. If I drive it down the driveway again, it comes on at exactly the same time, every time. Also, the front wheels on the 4x4 indicator are now flashing continuously as well...

I bought a non-contact thermometer and after letting the truck idle until warmed up and then driving up and down the driveway twice (2 miles) with the AT light flashing I checked the temperature on the trans. pan and it's about 145 F.

According to the service manual the temp sensor should have continuity at 289 - 304 F. With the exterior of the pan at 145, it seems impossible that the internal oil temperature is that high...

Thoughts? Maybe the TCM?

The ATF was pretty dark and the filter had some particulates in it, but not totally clogged. The pan magnets had a fair amount of pretty fine metallic residue on them.

By the way, I hope the Mitsubishi engineers added an exterior trans filter in later iterations. removing the oil pan was a PITA.