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OBD Codes > Ford > p0421

Ford Information

DATSC provides free error code information for Ford vehicles and is provided free of charge.

Facts
Country & Continent of Origin: United States (America)

Warm Up Catalyst Efficiency Below Threshold

PossibleSymptons

You will likely not notice any drivability problems, although there may be symptoms. The code may be more likely to occur after the engine has had numerous cold starts in the past 1-2 days.

PossibleCauses

A code P0421 may mean that one or more of the following has happened: The catalytic converter is no longer functioning properly An oxygen sensor is not reading (functioning) properly A sparkplug is fouled up

PossibleCauses

Measure the voltage at the oxygen sensor on Bank 1 (the rear sensor, or the sensor after the converter). In fact, it would be a good idea to test each oxygen O2 sensor while you're at it. One thing to note is that many vehicle manufacturers offer a longe

SpecialNotes

Basically this means that the oxygen sensor downstream of the catalytic converter on bank 1 is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.