You’re driving down the highway and something’s just not right.  You think it may be a transmission problem, but that covers a whole lot of territory because so many things that can go wrong with an automatic transmission.  Several of them will show up as a P0730 Error Code when hooked up to On Board Diagnostics (OBD), particularly a gear problem.

https://suntransmissions.com/blogs/news/error-code-p0730-incorrect-gear