MITSUBIS CODE P0421

2002 Mitsubishi Lancer

Tiny

MDJASIM

July, 22, 2009 AT 3:43 PM

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?

FOUND 23 RELATED QUESTIONS

Code P0421

9 ANSWERS
8 IMAGES

Po421 Code

1 ANSWER

1 Answer

Tiny

Docfixit

July, 22, 2009 AT 3:54 PM

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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