2003 Toyota Corolla code 420

2003 TOYOTA COROLLA
200,000 MILES • 4 CYL • 2WD • AUTOMATIC
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PREPCUTIE258
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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!
Aug 5, 2009 at 10:51 PM
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MHPAUTOS
  • ✓ASE Certified Mechanic
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  • ASE Certified Mechanic
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)
Aug 5, 2009 at 11:01 PM
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