i just put a full exhust system with no cat on my car and the check engine light came on an hour later i wanted to if i to flash my car

 

You will need to get an 02 simulator, or some sort of 02 fix. The reason you are getting the light is due to there being no cat. Getting a re-flash will not fix that. If you use the search function you can find the parts to make a manual fix, or you can purchase an electronic fix from a vendor.

Personally I did the manual fix with parts from autozone ($5.00)

 

why dont u put some effort into it and search? or go pull the code and dont be lazy lol... its just ur o2 seeing u have no cat

 

i have the manual and electronic o2 fix b/c the maunal did not get rid of it so i added the electronic. you will need to that though to get rid of the chcek engine light.

good luck