2002 Other Chevrolet Models catalyst system

Tiny
TERRYTEA
  • MEMBER
  • 2002 CHEVROLET
2002 Other Chevrolet Models 4 cyl Automatic

my check engine light was on. It came back as code
po420 catalyst system efficiency below threshold
bank 1 so I had a new catalytic converter put on
a month later my check engine light is back on with the same code
any idea why? I also had the 02 sensor replaced
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Saturday, October 11th, 2008 AT 2:49 PM

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Tiny
BLACKOP555
  • EXPERT
Try a new o2 sensor also check for exhaust leaks.

If the o2 sensor that monitors the catalyst efficency has failed will throw that code.

Also if the pre cat one or sensor one that monitors and adjusts the fuel has failed it may screw up the reading of the sensor 2 that mnoitors the convertor. Or it may have to rich a fuel mixture and cuasing the convertor to get too hot and burn out.
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Saturday, October 11th, 2008 AT 3:56 PM

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