RE: How do you no the catalytic converter in a 2003 chevy blazer is no good by Racquetball Champhttp://aolanswers.com/questions/catalytic-converter-2003-chevy_495395838455181/smog-tests-cat-bad-wopuld-getting_149439219940757?src=rss:qbp:qpbs<p>smog tests dont always show you if the cat is bad, first off you wopuld be getting a trouble code for catalyst efficiency. when the cat degrades the ability for the cat to change hydrocarbons to water and carbon monoxide to carbon dioxide weakens, as it weakens the readings of the front o2 sensor and the rear o2 sensor become more alike. also a temperature reading can be done before and after cat, the temp at the rear of the cat must be hotter than going in.  hope this helps</p>en-usRE: How do you no the catalytic converter in a 2003 chevy blazer is no good by Racquetball Champhttp://s1.anscdn.net/images/answers/aolanswerslogo_rmtaac1f83.gifhttp://aolanswers.com/questions/catalytic-converter-2003-chevy_495395838455181/smog-tests-cat-bad-wopuld-getting_149439219940757?src=rss:qbp:qpbs<p>smog tests dont always show you if the cat is bad, first off you wopuld be getting a trouble code for catalyst efficiency. when the cat degrades the ability for the cat to change hydrocarbons to water and carbon monoxide to carbon dioxide weakens, as it weakens the readings of the front o2 sensor and the rear o2 sensor become more alike. also a temperature reading can be done before and after cat, the temp at the rear of the cat must be hotter than going in.  hope this helps</p>RE: How do you no the catalytic converter in a 2003 chevy blazer is no good by Racquetball Champhttp://aolanswers.com/questions/catalytic-converter-2003-chevy_495395838455181/smog-tests-cat-bad-wopuld-getting_149439219940757?src=rss:qbp:qbpi<p>smog tests dont always show you if the cat is bad, first off you wopuld be getting a trouble code for catalyst efficiency. when the cat degrades the ability for the cat to change hydrocarbons to water and carbon monoxide to carbon dioxide weakens, as it weakens the readings of the front o2 sensor and the rear o2 sensor become more alike. also a temperature reading can be done before and after cat, the temp at the rear of the cat must be hotter than going in.  hope this helps</p>Racquetball ChampRacquetball Champmale41answer3.0Wed, 22 Feb 2012 12:59:45 GMThttp://aolanswers.com/questions/catalytic-converter-2003-chevy_495395838455181/smog-tests-cat-bad-wopuld-getting_149439219940757?src=rss:qbp:qbpi