which side is P0420? pre or post?

[J_STATUS]

P0420 which side of the engine? precat or postcat?

[JFP in PA]

P0420 is “TWC conversion too low” on bank 1-3. It is not an O2 sensor per se (assuming they both pass their own diagnostics), it is more likely the cat itself. OBD II manual says to clear it and see if it returns, if does, you need a new cat on that side………….

[J_STATUS]

So it's not the 02 sensor pre or post? I do have cat deletes. had it for 1 month then i just now got the code.

[JFP in PA]

That is your problem, the two O2 sensors are looking for the differential change the cat brings, and not seeing it, hence the "Three way catalyst conversion too low" code....... It may be possible to defeat this by having a PIWIS remap your DME to the RoW emissions spec (North American cars are the only ones running four O2 sensors [one before and one after the cat on each side], so the RoW map ignores the second sensor, ending the code).

You can still put the O2 sensors through their paces with a multi meter to assure yourself they are working, but I'd bet they are fine as this code is specific to the cat working, which implies the sensors are fine............

[Loren]

I believe it is only the Germany RoW map that ignores the second sensors. Either a PST2 or PIWIS can do this WITH your car's unique IPAS codes.

[RFM]

Since production year mid. 2003 all Porsche Europe ROW new cars are covered under Euro4 norm, which means that they use 1 pre cat. and 1 post cat. O² sensor on each cylinder bank as well. Since production year mid. 2009 is Euro5 norm in effect. On all these cars is not possible to run a Euro3 program.