Hi I'm new to this so not sure if I'm posting in the right spot but anyways I have a 2004 Infiniti g35 coupe with the code p0420 and the light inside of the car is (Service Engine Soon) the o2 sensors were checked and one was replaced catalytic converter was professionaly checked a few times oil and filter were both changed along with the air filter and the MAF was cleaned and nothing will solve this problem any ideas??? And also it has been checked for vacuum leaks and none were found.
My car has 94000 miles.
Hi there. First off, yes - this is the perfect place to post this type of question, so let’s try to explain the P0420 code and what typically causes it. When the oxygen sensors have readings that are similar to each other, it is an indication that the catalytic converter is not working as intended. If the voltage of the downstream oxygen sensor decreases, and begins to fluctuate like the upstream oxygen sensor, it means that the oxygen levels are too high and the Powertrain Control Module (PCM) will store the P0420 trouble code. You might want to read this article to review the possible causes and repair solutions.
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