Converter is not working as efficiently in Bank 1 and Bank 2 (two codes)...
P0421 - Warm Up Catalyst Efficiency Below Threshold (Bank 1)
Basically this means that the oxygen sensor downstream of the catalytic converter on bank 1 is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.
Symptoms: You will likely not notice any drivability problems, although there may be symptoms. The code may be more likely to occur after the engine has had numerous cold starts in the past 1-2 days.
Causes: A code P0421 may mean that one or more of the following has happened:
The catalytic converter is no longer functioning properly
An oxygen sensor is not reading (functioning) properly
A sparkplug is fouled up
Possible Solutions:
Measure the voltage at the oxygen sensor on Bank 1 (the rear sensor, or the sensor after the converter). In fact, it would be a good idea to test each oxygen O2 sensor while you're at it.
One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.
P0431 - Warm Up Catalyst Efficiency Below Threshold (Bank 2)
Basically this means that the oxygen sensor downstream of the catalytic converter on bank 2 is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.
Symptoms: You will likely not notice any drivability problems, although there may be symptoms such as a rough/hard idle when cold.
Causes: A code P0431 may mean that one or more of the following has happened:
The catalytic converter is no longer functioning properly
An oxygen sensor is not reading (functioning) properly
There is an exhaust leak
Possible Solutions:
Inspect for exhaust leaks. Next step is to measure the voltage at the oxygen sensor on Bank 2. In fact, it would be a good idea to test each oxygen O2 sensor while you're at it.
One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.
Hope this helps.
Basically this means that the oxygen sensor downstream of the catalytic converter
on bank 1 is detecting that the converter is not working as efficiently as it
should be (according to specs). It is part of the vehicle emissions system.
Check the O2 sensors and catalytic convertor.
Sorry, it is both banks due to the presence of the two codes. They mean the same thing but refer to Bank 1 and Bank 2 respectively.
meinverstand canyouexplain exactly what downstream means. I have a Mit Montero limited 2001 edition with a P0431 code. To buy an oxygen sensor for this car you are being asked if it is Bank2 driver's side before aor after the cat. Or Bank 1 passengers side before or after the cat. Please qhich one is this P0431 code. Thanks
@O2Sensor I'm not sure where it would be located off hand but the auto parts store should be able to tell you whether it is located before or after on your car.
What do i need to buy so that my montero sport does not have the p0421 code anymore? I just bought this car Do i need a whole new catilytic convertor?
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Hello not solved still problem Ok explained you everything began had problem het gasket was repaired but also has problem of the outlet that is in the canine to connect to charge the cell that towards which do not operate light Board doors is not blocked don't walk remote control course light of service this on but was then set service engine are and there gave me those code p0421 and p0431 No it is a result of the electrical problem
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