Question about 2002 Buick Century

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2002 Buick Century Code P0420

Had in-laws car checked @ the dealer for lack of power earlier on. Came back with back converter. They're price was too high so had done elsewhere. After replacement, getting code P0420, which is catalyst efficiency error. Did correct run time for cat to lite up, checked 02 operation and the post 02 sensor wasn't switching properly. Replaced. Week later still getting code. Checked for alternatives ie high octane gas. possible bad converter..but wondering if anyone has access to TSB's for the above vehicle. Wondering if there was a PROM update to reduce the sensitivity of the calculation for aftermarket 02 sensors, so the code doesn't set as much. Didn't get much help from the dealer service advisor when I asked him.

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  • Chris B Jul 03, 2009

    Yep I did that too fuel pressure is great

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Sounds as if yoou are actually having a fuel system problem.You need to rreplace the fuel filter and then check the fuel pressure. You should have around 50 psi. If the fuel filter stops up it will cause the exhast to starve for fuel and can damage a catalyst converter. You can get the fuel filter for about 15 dollars at any local parts house.

Posted on Jul 02, 2009

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Posted on Jan 02, 2017

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