i have a 2003 mitsubishi eclipse 4cyl few upgrades not much but a few weeks ago i took the a/c and power steering pump out well it was all fine till my check engine light came on i went to autozone to get a quick read it says my o2 sensor on the header is messed up has a heater malfuntion they said it could be a number of things but since that came on my fans dont work even tho i should still be able to activate the ac fan just by flipping a switch but that doesnt even work and it worked at first also it seems my fuel milage is a little worse