Auto Zone techs do not have the right reader to see if it is working properly. You need to take it to a tech. with something like a Sun Gauge not just a code reader. It has a graph to analyze the code or monitors in the computer system. Chevy or any good repair shop should be able to do it for you.

 

thanks

 

A bad cat' WILL NOT throw a CEL code. You will have a loss of power and bad tranny shifting. As far as I know, the only way to check one is to drill a small hole before and after the cat to check the diff' in backpressure. You have a 10 year/100,000 factory warranty on the emissions system.
I just threw a P0455 code ( I think that's it) evap' sys' major leak, and I checked my gas cap. It was NASTY around the seal area. Wiped it clean on both sealing surfaces, and haven't threw a code since.

 

thanks..i have a appointment with them 2morrow...should i print out something...will they charge me for the diagnotics?

 

What is this line pressure you are referring to?

 

Sorry for the delay CM. I haven't been on the site for a while. The 3 PSI was the pressure measured from the exhaust. My cat was plugged up.