CHEVY ENGINE CODE PO420

1997 Chevrolet Monte Carlo

Tiny

drz400s

March, 23, 2009 AT 5:33 PM

1997 Chevy Monte Carlo 6 cyl Front Wheel Drive Automatic 144, 00 miles
check engine light is on
engine code PO420
catalyst system efficiency below threshold ( Bank 1)
What does this mean?

FOUND 159 RELATED QUESTIONS

P0420 Cat Converter

10 ANSWERS
2 IMAGES

1 Answer

Tiny

rasmataz

March, 23, 2009 AT 5:37 PM

A code P0420 may mean that one or more of the following has happened: Leaded fuel was used where unleaded was called for
An oxygen sensor is not reading (functioning) properly
The engine coolant temperature sensor is not working properly
Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
Retarded spark timing
The oxygen sensors in front and behind the converter are reporting too similar of readings
Possible SolutionsSome suggested steps for troubleshooting a P0420 code include: Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
Inspect the downstream heated oxygen sensor (HO2), replace if necessary
Replace the catalytic converter

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