Hey everyone, first I'd like to thank you all for all the valuable discussions on this forum. I've been lurking for a long time and finally pulled the trigger. Many questions I've had already were easily answered by reviewing this forum. Sorry that my first post is a bit of a downer and super long!
A little background: I purchased a new-to-me 2016 MX P90D with 28k miles this week. We've been driving it around town in the Phoenix area with very hot temperatures all week with no issues. I even got lucky with the email alerts on the Tesla Wall Charger being back in stock and installed it in our garage. We've been using this to charge the car so far.
Today we took our first road trip driving about 100 miles north through the mountains on our way to Flagstaff before our first stop at a Supercharger. I noticed while charging the speed started at 96kW and quickly began degrading, eventually ending at 8kW by the end of the 40 minute recharge we needed. As soon as I pulled out I noticed a difference in acceleration. As I got to the entrance ramp on the highway, I realized I had so little power I couldn't get the car to accelerate over 40 mph and had to pull over. I also noticed a yellow exclamation point on both the power meter and the regen meter, as well as the gray lines had turned to yellow dashes, however no other alerts showed up. I was able to slowly accelerate on to the highway up to a decent speed while my wife googled the issue. We found it was likely the battery was overheated. I drove very conservatively in the left lane, but with the grades we were traversing, it didn't help. After a few minutes the power decreased to the point I had to pull on to the shoulder with my hazards on, since there were no exits for miles. My wife called roadside assistance and they recommended I pull over and let the car set for 30 minutes (not fun in 100 degree heat). We followed their instructions and turned the car back on, discovering the meters had returned to their regular colors. We began traveling on our route, but as we hit some of the steeper grades (max of 6%) the yellow exclamation point returned and the meters began lighting up yellow again.
We made it in to Flagstaff and got to our hotel and let the car set and cool off. We got back in about an hour later and headed to a Supercharger while we grabbed lunch. As soon as I disconnected the Supercharger cable and got in the car, I noticed the yellow exclamation point was back and the power meter was nearly all yellow dashes. We drove back to the hotel (very gingerly) and called roadside assistance again (3rd time today). This time he had us perform resets on the MCU, instrument cluster, and a vehicle power cycle. We thought this could help, but also realized the common denominator was Supercharging, so we drove back over to try it out.... No luck. As soon as I unhooked the cable, I got the same alerts. I was out of options as this point and our trip was ruined, so Tesla is towing it to the service center in Tempe.
I've been searching all over the internet for similar situations, but have found very few that match our circumstances. I hope the service center will be able to diagnose the issue, but all 3 R.A. reps we spoke to seemed dumbfounded. I wanted to see if any forum members have had this issue.