hi guys..anyone know about the p0420 code for 2001 maxima,,what it stands for,,
it may be one of my four o2 sensors and which one ..any information would be helpful ,,,got that code via auto zone ,,,but they erased my ses light,,

 

DTC P0420 THREE WAY CATALYST FUNCTION, BANK 1

The ECM monitors the switching frequency ratio of heated oxygen sensors 1 (front) and 2 (rear). A three way catalyst (Manifold) with high oxygen storage capacity will indicate a low switching frequency of heated oxygen sensor 2 (rear). As oxygen storage capacity decreases, the heated oxygen sensor 2 (rear) switching frequency will increase. When the frequency ratio of heated oxygen sensor 1 (front) and 2 (rear) approaches a specified limit value, the three way catalyst (Manifold) malfunction is diagnosed. Malfunction is detected when three way catalyst (Manifold) does not operate properly, three way catalyst does not have enough oxygen storage capacity.

Translation - The ECU thinks the pre-cat for bank 1 of the engine (the side by the firewall) is becoming plugged up. It most likely is the pre-cat but there are some other possibilities.

Possible Causes:

Three way catalyst (Manifold)
Exhaust tube
Intake air leaks
Injectors
Injector leaks
Spark plug
Improper ignition timing

 

thanks for the info,,i ll look into the possibilities,,