Check engine light on. O2 sensor problem. Loud rattling noise. on 2003 Chevrolet S10

My check engine light came on and I took it to an auto parts store. They said it was an o2 sensor. The truck makes a loud rattle underneath.Its louder with the a/c on. Could this be my catalytic converter?

by in Palmetto, FL on August 15, 2012
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1 answer
ANSWER by , August 15, 2012
Yep,time to replace the cat,with and the downstream O2.