Is P0421 a persistant code?
My s4 keeps turning on the servie engine light with a p0421 code. I have captured the live data for the O2 sensors and graphed them and found the lines to run paralell. (Leading me to believe both O2 sensors are operating pretty close to the same and that it is not an O2 Sensor issue, but rather a problem with the cat.) My question is, will the light eventually go off on it's own after a period of time? I know my A8 will throw occasional codes but eventually the service light goes out even though the codes are still present. I haven't driven the car long enough with the light on to see if it will go out on it's own.
Any advice appreciated.