rwetmore71Community MemberFebruary 12, 2021 at 2:04 am
Had the dealer diagnose the code said they checked everything sensors and so forth. All was good indicating the catalytic converter needed to be replaced. I had one ordered through a mechanic I know and had it installed.
2 days later the check engine light came back on. Again returning the P0420 code catalyst efficiency below threshold bank 1. What could be causing this?
Also, it has been suggested that the care has 2 catalytic converters. Is this true? Everything I have seen indicates it only has on and the care only has one exhaust pipe.old garage mechanicCommunity MemberNovember 10, 2021 at 10:45 pm
Cars after 1995 have sensors, the PO420 can mean the sensor after the converter or after the converter. It is telling you there could be something wrong with the exhaust readings. I would check the sensor before the converter first. That would give you the PO420 reading Look at the site the administrator wrote. It will tell you what code PO420 and PO421 mean.
MichaelHRitzelMSelleenAdministratorFebruary 14, 2021 at 2:06 am
Usually, you just have 1 catalytic converter for each engine bank. The P0420 code tells us it is the catalytic converter on bank 1. If you have a V-engine and two catalytic converters it will tell p0421 if it is on the other bank.
This trouble code can be very annoying to get rid of. In most cases, it is caused by a faulty catalytic converter but here is some more information:
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