Will not go into fourth gear

Hello,

It sounds like you have a transmission input or output shaft speed sensor that is going or is out. Lets confirm the problem by running the codes. Here is a guide to help you get started.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please let us know what happens, we are interested to see what it is.

Cheers, Ken