2003 Toyota Corolla code 420

Tiny
PREPCUTIE258
  • MEMBER
  • 2003 TOYOTA COROLLA
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 200,000 MILES
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!
Wednesday, August 5th, 2009 AT 10:51 PM

1 Reply

Tiny
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.

Mark (mhpautos)
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Wednesday, August 5th, 2009 AT 11:01 PM

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