Got red triangle and P lock error while driving on highway

I was on a road trip this weekend and all of a sudden while I was driving the red triangle came on and I got the P lock error message on the dash. After some research I discovered common causes are the 12v battery and the 7.5 fuse along with the blue wire in the fuse box, so I spent some time troubleshooting, measuring voltages etc. I have a good toyota battery that's less than two years old, even replaced it with an AGM from Oreillys to no effect. I have took all accessories off and even though I was getting voltage at the 7.5 fuse I went ahead and jumped it anyways to the blue wire and still nothing.
Attempted fixes:
New 12v Battery
Jump started in addition to 12v battery
Pulled and waited on 7.5a fuse
Pulled neg cable for 2min
Jump wired 7.5a fuse to Blue #4 wire in harness
Checked all fuses under hood
Stepping on and off of parking brake a lot
Power on off.
Evenually for some unknown reason it will shift and drive normally and get great mileage with no noticeable loss other than obviously cruise control with the red triangle. Any ideas for next steps? I build advanced electronics for a living so not opposed to diving into wires and fuses and relays and troubleshooting just need to know what to look for. Maybe the transmission control module I think someone had and that fixed it?

 

I'm getting a P3102 code. Also the park button flashes, when you get it running and shifting properly, it seems to go into park but there is no square on the dash to indicate that it is, the square is just gone.