My check engine light came on, so I went to AutoZone and got the code pulled. They send it was an o2 sensor. $80 later I was on my way home. It's too damn hot to change it now, so I'm going to do it tomorrow morning. The sensor that went bad was the one before the cat on my '99 Mitsu Galant. Can anyone give me a general idea of where it is on my car? Wanna kill these ads? We can help!