Indian Insstitute of Management actually checks all your academic scores along with CAT score but a decent score in CAT examination can surely give you a change to get one step closer to be a part of IIM institute. You will need to undergo the group discussion and personal interview rounds before finally you get to be called as an IIM student. So your personality basically can hide all these academic performances just bbecause if you speak smartly and present yourself in the best way there is nothing that can deny your admission.

Refer to the website below for more detailed information...

https://bschool.careers360.com/articles/iim-admission-criteria

Best wishes. Thank you.