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P0421 Diagnostic Trouble Code Discussion for August 2009

Warmup Catalyst Efficiency Low (Bank 1)

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Trouble Ticket Help Requests for DTC P0421
Help Request Posted
2001 Mazda 626 ES 2.0L MIL Lamp on VIN: 1YVGF22C91
P0421: Catalyst Efficiency Below Normal (Bank 1). ... aftermarket pre cat,but at $800.00,thats 1/2 the cost of the car,and what aftermarket cat would most use? I put a new O2 in for the customer,they said a parts guy said it would help,test drove and got all moniters to run,the EGR was last and as soon as all...
August 01, 2009