2002 Mitsubishi Lancer code P0421

Tiny
MDJASIM
  • MEMBER
  • 2002 MITSUBISHI LANCER
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 95,000 MILES
Failed in inspection coz code p0421: warm up catalyst efficiency below threshold (bank1) what does that mean and how to fix it?
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Wednesday, July 22nd, 2009 AT 3:43 PM

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Tiny
DOCFIXIT
  • EXPERT
Most likely CAT has deterated and needs replacement. In some cases it could be the rear O2 sensor but that should set P0137
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Wednesday, July 22nd, 2009 AT 3:54 PM

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