My 1999 chevy Monte Carlo, 87,000 miles
I have a p0420 on auto zone scanner, they said it could be a misfire or
oxygen sensor.
What could be problem. Thanks.                          







JK:
Hi. A code p0420 is catalytic converter inefficient. The converter is going to have
to be replaced. If no other codes, then that should take care of the problem. If
other codes, will need to get those repaired first as that may be why the
converter has failed.

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