hey everyone. my girlfriends 2000 mazda protege was setting off a check engine light. after taking it to auto zone the guy said that it was giving him a O2 sensor code. the engine doesnt appear to be running rough or anything like that, however.

is there a way to check the O2 sensor before just spending money on a new one? oh yeah, and where the heck is it? any help is greatly appreciated, thanks

 

O2 sensor should be located towards the end of your exhaust manifold. There should be a boss welded into the exhaust that the O2 sensor threads into. What the O2 sensor does is measure the content of the exhaust gases coming out of the exhaust to deteremine whether you are running rich (too much fuel) or lean (too little fuel). it adjusts the fuel/air ratio that the engine is using to run.

If you're O2 sensor craps out, your computer will go into a "closed loop" mode and will trip the check engine light. If it's giving you the O2 sensor code, the your O2 sensor is bad.

It shoud be as simple as disconnecting a wire harness, unscrewing the O2 sensor out of the exhaust and re-installing the new sensor.

 

You do have more than one o2 sensor BTW. There is one in front and one behind the catalytic converter. The one in front determines the proper fuel mixture while running. The one behind the converter measures the efficiency of the catalytic converter. You can also set a code for the heater portion of either o2 sensor even if the car runs fine. If you can get the exact code number it would be helpful. An example would be P0130.

I have a minor disagreement about this statement. If you have a major sensor problem, it will stay in open loop. It will enter closed loop if everything checks okay.