p0420 and p0430 at the same time!??!!

So I have searched far and wide on m3forums, zhpmafia, e46fanatics, and bimmerforums for information on throwing both p0420 and p0430 at the same time.

So far I have only come across one or the other. No one mentions throwing both the codes at the same time.

All issues with these codes that I read were fixed either under warranty or replacing all O2 sensors and/or Cats. Some threads dont even give a solution to one code! :confused:



I have a 2004 325i with 195k miles on it.

I do not know if the previous owner has replaced any O2 sensor or Cats.

(From the looks of it, none of the above have been replaced)

Maintenance wise, I know Pre-Cat O2 sensors need replacing every 100k miles, and from what I have read, the Post-Cat O2 sensors need replacing when they fail.

I have also read that these codes can be thrown due to other problems such as Air Intake, MAF, Thermostat, etc.



I have replaced all of the following at or around 150k:

Water Pump

Thermostat

Expansion Tank

All Serpentine Belts

All Puleys

Power Steering Reservoir w/ Hoses

Power Steering Pump

Oil Filter Housing Gasket

Valve Cover Gasket

Fuel Filter

BOTH Fuel Pumps



I threw both of these codes driving to the grocery store

I am confused as to why both Banks are being thrown at the same time.:hmm:

I am leaning towards a different problem rather than O2 sensors or cats since the codes were thrown at the same time.

Half of me wants to just buy new headers and a flash to just say %$#! it, but i do have a CA Smog Check due next month so i need a proper fix to this situation.



I will be trying to clean the O2 Sensors tomorrow and see if that makes any difference.





Any and all information and/or suggestions would be greatly appreciated.

I need this fixed ASAP