Ok, the other day I was driving on the freeway and got off and stopped at a light. Went to accelerate and noticed my Jeep was stuck in 4th. Had to shift manually. After I turned my car off and on again, it was fine until I drove on the freeway, then the same issue. Finally it threw code P0715.

First question- Which sensor do I need to change? I'm guessing output sensor?

Second- Turned my car on and backed out of my driveway the other day. Looked down and the check gauges light was on. The voltage was pegged all the way to the right. Tapped it and it went back to normal. Was driving today and all the guages started acting funny, jumping all over for about 30 seconds then stopped and was normal. Is this somehow linked?