P0420 2006 Nissan Altima

Asked by Jul 10, 2017 at 10:42 AM about the 2006 Nissan Altima 2.5 S

Question type: Maintenance & Repair

My check engine light never came on however my
car was having issues accelerating when pressing
the gas. It slowly picks up then catches and drives
perfect. Only when I brake does it take a slow bro
me accelerating again. Any who I got a diagnostic
test done and P0420 came up... NOW MY CHECK
ENGINE LIGHT IS ON. Does this mean I need a
complete new catalytic converter? Or can I use the
fuel injector and clean it out?

2 Answers


The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. Oxygen sensors are also referred to as O2 sensors. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). Catalytic converters are not normally a "wear" type item, that is they are not designed to wear out and need replacement. If they have failed, it is likely due to something else that caused it to fail. This is what a P0420 means in simplified terms.

2 people found this helpful.

Injector cleaner will not fix this... you more than likely will need to replace the Cat. Could be $200 if you DIY with a universal cat or around $1000 if you get an OEM / Pay for labor

1 people found this helpful.

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