Codes P0601 and P0880, transmission not shifting properly

Hello,

The code P0880 is likely the primary issue. One of the most common causes for that code is a loose connection to the TCM circuit. It can also be due to a faulty harness.

The best course of action would be to take a look at the possibilities.

I have attached the diagnostics guide for both of the codes below.
It has some insight and good information of what to look for.
Follow this guide as it can help you determine the issue.

Please let me know if you have any questions.
Thank you.

https://www.2carpros.com/articles/how-a-car-computer-works-pcm-ecm-bcm