I live in A county where you have to have emissions to get a tag and my car won't pass emissions becuase of code 420 which is "catilist system is running below threshold (bank 1) and I am wondering what exactly that means i'm not sure if that means I need a new catalistic coverter or it could just be an 02 censor. If you could be any help that would be great! Thanks!
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Wednesday, August 5th, 2009 AT 10:51 PM
1 Reply
MHPAUTOS
MECHANIC
31,937 POSTS
Hi there,
you will need to check the cat converter, the 02 sensor and the wiring to to ECU, as this is a heated O2 sensor, I would check this function first.