What Does A OBDII Code Of P0420 Catalyst Efficiency Below Threshold (Bank 1) On A 2002 Monte Carlo Mean?


2 Answers

Anonymous Profile
Anonymous answered
Causes 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
jk Tech Profile
jk Tech answered
This code is almost always the result of the catalytic convector being inefficient- and needs to be replaced. Looking at live engine data is needed to be be certain. Warranty of these is up to I believe 80,000 miles, may even be up to 100,000.

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