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P0421....Take a look PLEASE!!! >

P0421....Take a look PLEASE!!!

Audi A4 The Audi A4 model offers nimble handling and performance that makes it one of the leading cars in its class. Read more about the Audi A4 in the Audi A4 review.

P0421....Take a look PLEASE!!!

  #1  
Old 07-10-2012, 03:52 PM
1st Gear
Thread Starter
Join Date: Dec 2011
Posts: 42
Default P0421....Take a look PLEASE!!!

I recently changed my spark plugs on my 2003 audi a4 3.0L avant.
I did the work myself and took my time doing one at time.
I used the OEM plugs.
Everything was fine for over a month.
Then the dreaded Check engine light came on.
Code P0421
Says Warm Up Catalyst; Bank 1: Efficiency Below threshold

Do you think me changing the plugs caused this light?
Whats the normal fix?
Just need a new Cat?

ANY ADVICE MUCH APPRECIATED HERE!!!!
THANKS!
 

Last edited by 2003audiA4avant; 07-10-2012 at 04:01 PM.
  #2  
Old 07-10-2012, 04:00 PM
1st Gear
Thread Starter
Join Date: Dec 2011
Posts: 42
Default

OO btw I used the fuel cleaner REDLINE!
I just realized that I used it on the tank right before the CHECK ENGNE LIGHT went on. Maybe the fuel cleaner caused an excess of fumes on this next tank??
 
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