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Cat Code PO420 / 16804

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Old Jun 6, 2008 | 12:44 PM
  #1  
madrasautoparts's Avatar
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1st Gear
Joined: Oct 2006
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Default Cat Code PO420 / 16804

My 2002 A4T has had a on going service lite issue. Code PO420.
I have replaced both oxy sensors with oem bosch. Code returns within 15 miles.
I then replaced the Cat converter with Oem new. Code returned again . Replaced the trailing oxy sensor. Code is back..? Any one faced same issue..? Car has 104,000 miles. Not an oil user. But it did incurr the oil sludge problem.
Thankyou
Cory
 
Old Jun 7, 2008 | 07:28 PM
  #2  
CRAZYHAWK's Avatar
4th Gear
Joined: May 2004
Posts: 4,078
From: Northern NJ USA
Default RE: Cat Code PO420 / 16804

Try Seafoam in the gas tank, and through a vacuum line.
 
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