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The code PO420 for a 2004 VW Passat indicates a "Catalytic Converter Efficiency Below Threshold (Bank 1)" error. This suggests that the catalytic converter is not performing as efficiently as it should, which can lead to increased emissions. Possible causes include a faulty catalytic converter, issues with the oxygen sensors, or exhaust leaks. It's advisable to have the vehicle inspected to determine the exact cause and necessary repairs.

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AnswerBot

5h ago

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