99 MGM o2 sensor check engine light

Check engine light is on. I had the code read at Auto Zone AND Advance Auto Parts (just to make sure I got the same answer from both). They said the code indicated there was a prob w/ the o2 sensor but the reader didn't specify which one.

1st question: is there a way to tell which is malfuntioning (hopefully w/o having to go to dealership;

2nd Is this an intallation that I can perform?

Thanks, in advance!
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Design Host (http://hostndesign.com)

I believe there is a way to test with a multimeter. The voltage should be switching between 0 and 1V at a regular interval.

You can replace them yourself. The H02 sensors (before cats) are a bit harder since they're in a somewhat tight space.

If you can go back to Autozone and get the exact code, we can see which O2 sensor is failing.

After posting this, I cleaned my K&N air filter. While waiting for it to dry, I sprayed/cleaned the Mass-Air Sensor... The chk eng light has been off, since then.

I went back & talked to the manager @ AutoZoneit (who actially knew what he was talking about)-- turns out that BOTH auto parts stores gave half-assed info: they should have told me that the code that the reader gave indicated that the problem COULD be the c02 sensor.... OR something else (like the Mass Air Sensor[!!!!])
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Video Review (http://videoreviews.org)

When you have the codes read at the parts store, get the exact number and post the number back here. With the exact number we can search our information ang dive you a real close guesstimate as what the problem is.