Failing to change gears when on Automatic mode

Hello my name is Dave.

It sounds like the most likely culprit is your transmission output speed sensor. The fist step in determining if this is likely would be to pull any trouble codes stored in the PCM. I have attached a link to our tutorial on retrieving trouble codes, please keep in mind that even if the check engine light isn't on there still can be codes stored in the PCM.

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

If you could find out if there are any codes and get back to us on your progress we can guide you further. We look forward to hearing back from you and thank you for using 2CarPros!