P0420 fault code anyone else had this ?
 

The bug wagon threw up a cel code yest found out today it's p0420

Spoke to the guy who scanned it for me he said check the vacuum pipes first as I have just had a major service and maybe a mech had dislodged a pipe what else could it be because I can't hear any air loss from them cheers

P0420 is an inefficient CAT code.

Is the car fitted with a sportcat or decat ?

I believe it has a prodrive sports cat as it has the PPP package would this be the likely cause then I suppose it would now fail an emissions test

If it's a WRX it wont have a Prodrive sports cat fitted as part of PPP. ;)

If you have had one fitted it can cause that fault code, did on mine anyway.

Ok I thought the sports car was part of the package then no just a normal cat is there a way of telling I'll get under and have a look

Did you solve this? I have a STI with a prodrive sports cat and the same code. would it be the sport cat that is causing this or could it be something else like the front o2 sensor?

I have a 51 plate bugeye wagon and the CEL came on last Saturday whilst going up the M1 (it remained solid which suggested it wasn't detrimental). I got off at the next available junction and checked the obvious things. It was evident I'd let the oil level slip - suffice to say it was short of oil. I got the car to the next available services and chucked in some 10w40, and then decided to return home just in case something more serious was wrong.

I purchased an OBDII reader that same day with a view to checking the code and seeing if it was something I could sort myself - would've expected the oil light to be illuminated for problems with oil. However, before the reader arrived, and after a few days of normal journeys, the CEL went out, so on the surface it appears that the [lack of] oil [pressure ?] triggered the CEL, and the ECU corrected itself as a result of me correcting the oil level.

Still curious about what code the ECU actually generated I plugged in the OBDII reader and it had recorded a P0420 fault code. Not sure how low oil would trigger that really (guess it might not actually have been the oil at all ?).

Anyway, having done a search on scoobynet it seems that people have encountered the P0420 (and other related codes) as a result of a number of different causes, but one of the most frequent that keeps coming up is a faulty neutral position switch on the gearbox eg:

https://www.scoobynet.com/general-te...2-and-4-a.html

:Suspiciou

Lambda sensor most likely. These get coked up on all modern cars.
Take it out, submerge it in a cup of diesel over night and see if it cures the issue.