Question about 2002 Volkswagen Passat
I am trying to diagnose and correct this code.
VW Passat V6 trouble code 421,
This is a common problem with V6 Passats. VW put out a TSB on this a few years ago.
The code is telling you that your catalytic converter (driver's side, I think) is bad. It's more than likely not bad.
VW put out a TSB on this a few years ago. TSB 05-13. The cause of the error code is basically an over sensitive ECU (computer of car/engine) and the fix is to have your ECU flashed with the latest and greatest software. Depending on your mileage they might do it under warranty - you'll have to check.
It's still possible that it might be a bad catalytic converter - and the dealership might try to tell you that either way. Call VW (1-800-822-8987) and ask them about the TSB (I couldn't find it online).
Tell the dealership you want the ECU flashed - it's much much cheaper than a cat. No sense replacing it if it's not bad
There is a federal warranty on catalytic converters - 8 yrs or 80k miles...
Hope this helps!
Please rate/vote for me!
Posted on Jul 18, 2009
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Posted on Jan 02, 2017
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