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P0421 Diagnostic Trouble Code Discussion for September 2005

Warmup Catalyst Efficiency Low (Bank 1)

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Trouble Ticket Help Requests for DTC P0421
Help Request Posted
1997 Mitsubishi Galant ES 2.4L MIL Lamp on, VIN: 4A3AJ56G4V
P0421: warm up catalyst below efficien. light came back on 2 weeks later same code, so cleared light , put som techron in it ,and beat the snot out of it, extended high speed , w/full throttle load shifts, car runs like wild deer, this is a low miles vehic driven by old lady, cats are coo coo money,...
September 02, 2005