VAG-COM Code P0421 Help (2002 Allroad 2.7t)

[YKallroad]

Was going to post this on the AudiWorld Allroad forum, but it appears to be having issues this morning, and I know there are some VAG-COM gurus here too.

Repeatedly getting CEL after startup. VAG says it's:


Googling says that it could be the catalytic converters, or something related to that, such as the secondary air injection system (my SAI pump does make a huge noise on startup.)

Has anyone encountered anything similar to this? How do I start troubleshooting it?

[N'Syncro]

Re: VAG-COM Code P0421 Help (2002 Allroad 2.7t)

I've got the same code (but also 16815 as well - Bank 2). Pretty sure our cat's are kaput. Mine came up last year right after I was at the track with some unleaded 99 octane race gas. Must have cooked them which is BS b/c they're Milltek's.

My clutch is starting to go on me, so when I replace it, i'll probably just cut out the cats and replace them with universal aftermarket ones.

Not much we can do about it, other than trying to add some spacers to your rear o2 sensors but it probably won't help... Or get the CEL coded out.