CEL P301 & traction control light on
 

Hi, about two weeks ago I put on a Corsa catback exhaust on my 2018 Brz without any having any issues. After about a week of installing the catback I started getting CEL Code P301.

The car only has 17K miles on it so I'm a little shocked if the spark plugs or injectors are going bad.
The car starts rough on cold starts but after 10 seconds of warming up the car run smooth. The code goes away if I erase it with an OBDII but usually comes back after having a cold start.

Two days ago the car started over heating. Sometimes the car overheats when driving but after 3-5 seconds of the overheating light blinking; the temperature drops back to the middle.
Both radiator fans kick in and the LH one is always on when in idle.

Did anyone else had a misfire when changing their catback?

usually a 301 code is amiss fire in #1 cylinder might have a bad coil or spark plug it happens as far as over heating check your coolant level to see if there is enough coolant if so may want to take it to the dealership if you still have a warranty

Has your car been tuned? If so load the stock tune back in. If the problem goes away obviously you have a tune issue. If not then take it back to the dealer for warranty. A cat back will not cause an issue like that. Hopefully the dealer wont be an ass and realize that also.

I haven't tuned the car yet. I didn't think a catback would cause problems with the air fuel ratio or any other issues. When installing the catback the gasket was a little bent but I didn't think it would cause a problem since it bolts on tight. I haven't tested for an Exhaust leak but in the event that there is one I don't see how a exhaust leak from the catback would cause a misfire.

I'm going to try swap the coil and spark plug and see if that's the issue. I find it rare for it to be the cause of the issue since it's still "new", but you can never be sure until you try.