I just recently bought a 350z 2007 base. The check engine light was on when I bought it. I took it to get checked at auto zone and they said that both O2 sensors needs replaced. I noticed a rasp in the exhaust so this tells me the exhaust is not stock. Im wondering if the CATS are removed causing the O2 sensors to read wrong throwing the check engine light. My question is would the check engine light be on if the CATS are removed or would this no cause this. If this would not cause this I guess I will just get them replaced.

 

If the cats are removed then yes, it would trigger a cel unless defoulers are installed with the 02 censors.

Jack up the car and take a look to see if you have cats or test pipes.