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Possible causes- Warm Up Three Way Catalytic converter deterioration or malfunction - Exhaust system leaks - Loose front or rear HO2Ss - Faulty front heater O2 sensor - O2 sensors harness is open or shorted - O2 sensors poor electrical connection
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po421 catalytic converter code [warm up catalyst efficiency below threshold bank 1] means the o2 sensor is detecting low oxygen in exhaust problem can be cat conv going bad---o2 sensor faulty-and or bad spark plug ....as to the p0441 evap system[-evap emissions control system incorrect purge flow ] this is a system code meaning any part of the evap can have problem will need to check the fuel lines vapor lines for damage or breaks-check purge valve -purge valve solenoid- canister- and vacuum lines
Have there been any driveability or performance issues with the vehicle, have there been any recent repairs or tune-up work performed, if so was the check engine light reset and were the codes recorded on previous repair orders.
Do not rely on scan tool data alone. In most applications, the customer will have the check engine light reset prior to repair. If the original cause of converter failure is intermittent, only the catalyst failure code may show up (masking the original reason for converter failure).
Have there been any driveability or performance issues with the vehicle, have there been any recent repairs or tune-up work performed, if so was the check engine light reset and were the codes recorded on previous repair orders.
Do not rely on scan tool data alone. In most applications, the customer will have the check engine light reset prior to repair. If the original cause of converter failure is intermittent, only the catalyst failure code may show up
warm-up catalyst efficiency below threshold [bank 1] means the o2 sensor after the cat converter is detecting that ur cat is not working up to specs [correctly] can be a fouled plug-faulty o2 sensor- or cat converter is starting to go bad
you have the same engine as my 2003 Galant, this should help... http://www.alldatadiy.com/alldata/AFI~V11366605~C40797~R0~OD~N/0/89012112/98644464/98644470/110938985/34853741/34857029/34857030/34857663/122915129/135964338/135975025
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