GRD1977

P0420 Catalyst System Efficiency Below Threshold (Bank 1)

2006 MDX. Getting this code and failed emission test. It refers to Bank 1. I have searched online to find out which side is bank 1. So I can order the part and get it installed.

Please advice about the part.

Thanks.

Jono Lach

I just bought an 03 mdx passed safety and emissions ... Got it friday and started driving it saturday... Laatnight the engine light come on and 2 codes appeared ... P420 and something about the 02 sensor ... From what my mechanic told me is that a battery change should fix it. Going to buy one thursday so ill see what happens

thoiboi

Unlikely... But hope it works! P0420 is usually the cat..

Jono Lach

I checked the battery its fine charge is good etc. This was just etested friday and the light goes on 2 days later ...

Is it possible the person i bought it from erased the codes brought it in to get emission done and it passed or is there a way for the emissions testers to know if codes were cleared. Cause if thats the case im gonna be heading back to the seller asap

Sorry for late reply.

Thx

thoiboi

No, at up and up smog shops, if the check engine code was on and cleared, when they plug in the OBD scanner, it'll have a "Emissions Monitor not ready" flag that will cause the smog to fail.


Very likely that they went to a shady smog shop

thoiboi

But it could also be bad gas, Are you using a top tier premium gas? it could also be the o2 sensor being lazy or fouled up.