I got a PO420 code

Tiny
SHEPPERDNOVEMBER
  • MEMBER
  • 2000 CHEVROLET S-10
  • 88,500 MILES
I got a po420 code. 9k on a new GM crate engine.(The last owner did not believe in proper service)New cat(Walker). New 02 sensors(Bosch).I checked for leaks(vacuum and exhaust). None found.I cleared the code and have rechecked for active or pending codes every 2 days for over a month. None found. MPG and performance are great. Could the aftermarket cat and/or 02 sensors have anything to do with it?(False code?)Or is it just a fluke? Thanx Shep. (Retired tech trained on asian imports)
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Monday, February 18th, 2013 AT 3:58 PM

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Tiny
SHEPPERDNOVEMBER
  • MEMBER
Sorry I forgot to tell you. It's a 2.2L 4cyl.
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Monday, February 18th, 2013 AT 4:57 PM

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