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P0421 Diagnostic Trouble Code Discussion for January 2020

Warmup Catalyst Efficiency Low (Bank 1)

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Trouble Ticket Help Requests for DTC P0421
Help Request Posted
2016 Mazda CX-5 Touring 2.5L MIL Lamp on VIN: JM3KE2CY1G
P0421: catalytic convertor. ... on, code p0171 p0421 install a/f snsr per tsb 01-010/16 the light came back on p0171 only code. we had smoked system no leaks found, fuel pressure are good. the one thing that we keep seeing is ect 2 is -40 while ect 1 reading normal, ect 2 is the snsr...
January 10, 2020