Got the 0509 code (Front Left 02 sensor) after installing a y-pipe like 6 months ago. Reset the ECU a few times and it would stay off for a while then come back. Finally went and bought a new O2 sensor (Bosche) and replaced the bad one (front left bank, which is the one closest to the front of the car). Reset the ECU, everything seemed fine. Now 3 days later the CEL trips again with the same damn code! Doesnt seem like I'm getting bad gas mileage or having any misfire issues...any ideas!?

shaz

 

anyone? Bad ECU, dirty pipe, new O2 sensor is bad? anyone had this happen?

shaz

 

CEL tripped again today. Only took about 20 hours since I reset it. I guess I'll just run a tank of gas and see what kind of mileage I get...

 

CEL light has been on for a week, I didnt reset it. I got my normal mileage for a tank of gas...around 365 miles, so it seems like the O2 sensor is working fine. Anyone think maybe the ECU is messed up, or the CEL itself??

shaz

 

365 isn't low to you?
i don't think i have ever seen an ecu go bad, if ur o2 sensor has a warrenty get a new one and try it

 

like I said, I've already replaced the O2 sensor. And no, 365 miles for a tank is what I always have gotten. I mean, there's still some gas in the tank when I fill up...maybe .5-1 gallons

shaz