Trying to determine if it's a bad sensor or a real transmission issue:
I left the Transmission Temperature Gauge on display during my drive home and this is what I observed. The thermometer on the gauge bounced up and down at times, between the temperature readings. My fastest speed was 40 with traffic. I watched this gauge continue to rise up to 224 degrees going up the mountains and still experiencing some sputtering.
As I continued on my drive, it started raining and traffic slowed a bit. The temp outside had cooled off to 66 degrees. I watched the Transmission Temperature Gauge drop steadily down to 136, where it stayed on my drive home. I could not film this, needing two hands on the wheel for curves.
It is now 9:05am, Tuesday morning. The temperature outside is now a cool 70 degrees and the Transmission Temperature Gauge is reading "H" and I've not even started the car! This USUALLY prevented my car from starting, but a new fuel pump module and fuel tank wiring harness has been installed and she started right up!!!