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P0421 Diagnostic Trouble Code Discussion for July 2010

Warmup Catalyst Efficiency Low (Bank 1)

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Trouble Ticket Help Requests for DTC P0421
Help Request Posted
2003 Mazda Protege ES 2.0L Poor Idle Quality, Surge, Misfire, MIL Lamp on VIN: JM1BJ22553
P0421: Warmup Catalyst Efficiency Below Normal (Bank 1). Hello, this vehicle came in for an overheat issue and found that it has a real hard time idling. Scanned the ecu and got 0300 misfire code, 0117 ect code(overheat), 0171 fuel system lean, also found that at normal operating temp. Fuel system is still in open ...
July 26, 2010