Oxygen Sensor, upstream vs downstream

[buddhawarrior]

Hi all,

I am replacing an Oxygen sensor, and the one I needed is the one further away from the engine, which I assume is the "downstream" one. I purchased a denso aftermarket downstream one. But It looks more like the OEM upstream one.

Am I getting the two confused? What's the difference between the two? How can you tell?

one other note. I don't have a car computer, so I can't see if it fixed the issue, or if there are other issues. Cause the check engine light is still one. I'm wondering if the check engine light will go off if the problem has been fixed, or If I need to use a computer to clear the code.

Thanks,
Thomas

[redmondjp]

How do you know that the downstream sensor needs to be replaced? Did you have a shop scan the stored trouble codes for you?

It would be helpful if you provided the code(s) to us so we know how to help you. Just throwing a new oxygen sensor at the car may not do anything at all to correct the issue.

[aaronm]

Disconnect the battery for a little while and the light should go off. Many auto parts stores will loan you a code reader for free. If the problem is fixed, the light will go out soon even if you don't disconnect the battery.