2002 MITSUBISHI LANCER CODE P0421

  • Tiny
  • MDJASIM
  • 2002 Mitsubishi Lancer

Computer problem
2002 Mitsubishi Lancer 4 cyl Two Wheel Drive Automatic 95000 miles

Failed in inspection coz code p0421: warm up catalyst efficiency below threshold (bank1) what does that mean and how to fix it?

Wednesday, July 22nd, 2009 AT 3:43 PM

1 Answer

  • Tiny
  • Docfixit
  • Expert
  • 18,991 posts

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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