p0404 and p0420
September 1st, 2013, 7:31 PM
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p0404 and p0420
Ok, so my inspection is due, took it to a mechanic and he says I need a new cat, I would like to verify that on my own. I am throwing a p0404 and P0420 code. I replaced the egr valve 2 months ago and immediately afterward i noticed the cars rpms would jump ever so slighly at highway speed, but never did prior. I have my own actron scan tool, but don't fully understand the live data. Are there anyways to tell if my Cat Converter has gone bad? I know the basic symptoms, smell, rattle, cherry red, None if which I have. I was thinking it could be my upstream 02 sensor?
Not to sure though any opinions are appreciated
Not to sure though any opinions are appreciated
September 1st, 2013, 10:59 PM
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PO 420 is almost always a bad cat. If you want to look for yourself the look at the upstream and downstream O2 sensor data. If the voltages mirror each other then you have a bad cat. Upstream o2 voltage should fluctuate above and below 500mV always, downstream o2 should fluctuate below 500mV when the cat is working.
September 2nd, 2013, 2:26 PM
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Ok So I cleared the codes yesterday, cycled it and the 404 is no longer there. p0420 has come back after 40-50 miles.
Heres a few posts of the live data
Heres a few posts of the live data
Last edited by HOMESLICERYRY; September 2nd, 2013 at 2:29 PM.
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