The P0420 code signals a low catalyst system efficiency problem. This code suggests that the oxygen levels are below the desired threshold (Bank 1 or Bank 2), which most often results from problems with your car's exhaust or fuel systems. It can sometimes be tricky to diagnose.

Here are the three top fixes for the Honda / Acura P0420 error code.

• Catalytic Converter Cleaner – Can be purchased at Walmart. I prefer the Dura Lube Catalytic Cleaner for around $20. I put it in the car with a half tank of gas. Sometimes you need to repeat this process if the light still doesn’t go off. If after two cleanings the problem still isn’t solved, move on to number 2# below.

• Wash the Catalytic Converter – Remove the Catalytic Converter – Fill a large bucket with half cup of Dawn Dishwashing Liquid and hot water. Let soak for 10 to 15 hours occasionally sloshing the dishwater through the converter.

• Clean and Modify the Oxygen sensor – Remove the Oxygen sensor and let soak in carb cleaner overnight, then modify the sensor by purchasing a spark plug non-fouler (2 for $20 at Walmart), drill out the bottom of the non-fouler with a ½” drill and then install the non-fouler between the sensor and converter.

Lastly, use a scan tool to clear the P0420 error code.

Using all three methods above will cost you less than $50 and will fix around 90% of the vehicles that come in with this error code. Home the helps.

 

Which one is bank1 and bank2.

 

Which one is bank1 and bank2.

my post was a incorrect. Had code on Bank one sensor 1 Found it was a bad converter from there stock. Replaced again and all is good still. Note. Replaced sensor 2 - contaminant from bad converter particulate clogging the ports

see photo.

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Perhaps you are plagued with the VCM issues that are causing excessive oil consumption and that is ruining your catalytic converters? I had this issue on the 2010 I owned.

A VCM Tuner device can help, look into them. I have one for sale if you are interested - PM me.