Rick's Free Auto Repair Advice

Posts Tagged: P0420 code

P0420 caused by bad O2 sensor?

P0420 can it be caused by a bad O2 sensor? Does a bad oxygen sensor cause a P0420 code? Rick: Not really You: but everyone online says to replace the oxygen sensor to fix a P0420 code. Rick: A lazy oxygen sensor can cause the ECM to command overly rich/lean air/fuel mixtures and prolonged operation in that mode can damage the catalytic converter. BUT, the ECM is also programmed to set an O2 sensor trouble code when it detects long periods of slow O2 sensor response. The parameters were much … Read More


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