Home › Forums › Stay Dirty Lounge › Service and Repair Questions Answered Here › 2002 buick century p0420 › 2002 buick century p0420 April 18, 2012 at 11:00 am #438370 college manModerator the code p0420 happens with these after market cats. due to there high flow capabilities. the 02 sensor can’t pick up the flow to read it.C8-) so the computer throws the code.
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