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Old 01-08-2011, 04:20 PM   #21 (permalink)
Ford Man
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Originally Posted by nemesis View Post
Check engine codes do not tell you which part is bad, they tell you what's being affected. Just for the future reference.
This may be true in some cases, but PO420 usually does indicate a bad converter. I think the the definition for the code reads something to the effect of "insufficient catalyst efficiency" meaning the 02 sensor detects a problem with the polution in the exhaust gasses. The codes are there to steer you in the right direction of things to look into. Yes, it's possible to have certain codes that will give you several things to check that may not be the fault, but could contribute to the problem. Several years ago I took a car in for emmisions testing (tail pipe sniffer test) and the readings maxed out the emmisions testing equipment (pre OBD II) and the problem was a bad vacuum line.


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