Topexec

my '02 a6 4.2 is throwing out CELs PO421 (catalyst below threshold bank 1), PO431 (catalyst below threshold bank 2), & PO441 (EVAP small leak). the car gets loud around 30mph but doesn't have the tell-tale "rotten eggs" i've heard of when cats go bad.

took it it mcgrath audi in glenview,il and they quoted 4k to replace the 2 cats. could they have misdiagnosed? or would aftermarkets be a cheaper alternative? another what do you guys think?

MarkW

Just don't let the dealer replace unless you can get it under warranty

Topexec

Sorry, forgot to mention car has 90k miles, so no longer under warranty

V8BOB

My wife 2000 Passat with 2.8 V6, 70k miles, had the same issue. Turned out there was a software update and VW reflashed the ECU. From what I understand, the ECU was overly sensative to the temperture of the cats during warm up. The software update corrected that. $0.00 under warranty, $100.00? out of warranty. No more CEL.

Reifle

Had them replaced at an indie with Magna Flow - car runs really well and still no CELs. Once off the car the old cats the guts just fell out!. High flow cats and the labour was less than $300.00 CDN. My gas milege improved slightly after the cats were done.

4Driver4

Same here on my A4 - also 2000 with a 2.8. Of course, I had to pay.

paulroad

much less $$ and usually better diagnosis.

snowcat

My 2.8 did the same thing and they flashed my ECU and the codes stopped. Saved $$$.

btruby

TJ! Does anyone know what size the inlet/outlet piping is on the stock cat? (2.8)

absolutcq20v

And those codes *could* be generated as a result of a evap. system leak.
Can't hurt to find a second opinion from an Audi/VW-specific independent mechanic. Good luck.