Why is car throwing P0121 code even after replacing throttle body?

What is your question?

The check engine light came on and the car went into limp mode. The code it is throwing is P0121. When I shut the car off and restarted it it drove fine but the check engine light stays on. After starting the car two or three times to check engine light goes off and it stays off for a few days before it comes back on and goes into limp mode. I did replace the throttle body but it still does the same thing. What else can I do?

What makes this problem better or worse?

When it's in limp mode I can pull over and restart the car and it'll drive fine

How long has your 2013 Kia Optima had this problem?

A couple months