I'm a newbie, and have read the entire excellent 4th Gen. FAQ. Thanks to all of you, I have learned a lot about my car over the last two days.

My Check Engine Light came on. Checked the code (o2 sensor), then immediately reset the ECU before changing the sensor. My plan was to see if the CEL came back on, working on the theory that, if the O2 sensor really is bad, the CEL will come back on at some point soon.

Is that a mistake? By resetting the ECU with a bad O2 sensor, did I accidentally tell the computer that the bad reading it's getting from the sensor is normal?

 

That was not a mistake. Wait and see if you get the same code back. If the o2 is really bad, your ECU will continue to throw the CEL light no matter how many times you reset it.

 

It won't throw it again. I had a bad front-right O2 sensor and I reset the ECU. 2 months later still no code even thought I am positive the sensor is bad. Actually just replaced it this morning...

 

it WILL throw it again. if the CEL comes back on, try cleaning it. if that doesn't help, just replace it.

 

how do you clean an o2 sensor? my cel keeps going on after resetting it and it says my front left sensor is bad and i want to make sure i have to buy a new one since i'm in college and dont have much money. thanks.

 

Viet_racer, when the CEL relights, does the ECU show the same code for front left sensor (0303) again? That was the basis for my original question.

 

Listen to what njmaxseltd said.

 

try SEARCHING.....

 

Haha sorry about that. Yes my CEL keeps going off with the same 0303 code so I guess my O2 sensor is bad. I didn't read njmaxseltd's post correctly cause I was on the phone while reading it. Sorry about that.