What does it mean?
The powertrain control module (PCM) is the computer that controls everything to do with the engine and it is receiving information that the catalytic converter on bank 1 is not working as well as it should.
There are three things you will need to know in order to understand what this code really means: The purpose of a three-way catalytic converter(TWC) What an oxygen sensor(O2S) is How PCM monitors catalyst operation Exhaust gasses from automobile exhaust, in general, are harmful to the environment. Three gases in particular are the most harmful; Carbon Monoxide(CO), Hydrocarbons(HC), and Oxides of Nitrogen(NOX). The purpose of a TWC is to eliminate as much of these three gases as possible.
When exhaust gas leaves the engine it is extremely hot as it enters TWC. When these gasses and oxygen come in contact with the platinum catalyst they are reduced to carbon dioxide (co2) , water(H2O) and nitrogen oxide(NOS). In this process the amount of oxygen is also reduced. An oxygen sensor is a ceramic sensor located in the exhaust pipe both before, upstream, and after, downstream, of the catalytic converter.
The sole purpose of these sensors is to measure the amount of oxygen in the exhaust gasses and send this information to the PCM. On four cylinder engines there are generally two oxygen sensors; Bank 1 sensor 1 and bank 1 sensor 2. On v6 and v8 engines there is an additional two sensors; bank 2 sensor 1 and bank 2 sensor 2. In every application, regardless of bank number, sensor 1 is always upstream of the TWC and sensor 2 is always downstream.
The PCM uses the oxygen sensor information to determine the amount of oxygen entering and leaving the catalyst. The amount leaving should be significantly less than amount entering; that difference is a direct reflection of how well, or efficient, the catalyst is performing. By combining the input of other engine sensors and the amount of fuel being injected the PCM expects to see a predetermined amount of difference in the oxygen content.
When that difference falls below the predetermined amount the PCM turns on the check engine light and sets P0422 in memory Armed with this knowledge let’s take a look at some causes, some quick tests and some possible solutions for diagnostic trouble code P0422.