Transmission is shifting hard, and the Check Engine Light turned on

Hello,

The check engine light gets triggered when the on-board diagnostic system detects any fault.
This could be due to any number of components or sensors.
The best course of action would be to scan and retrieve the code(s) first.
Most auto parts stores have scanners that can be used to get the codes.

Take a look at this helpful guide:

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

Let me know what you find or if you have any questions.
Thank you.