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P0421 Diagnostic Trouble Code Discussion for October 2008

Warmup Catalyst Efficiency Low (Bank 1)

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Trouble Ticket Help Requests for DTC P0421
Help Request Posted
2002 Mitsubishi Lancer ES 2.0L MIL Lamp on VIN: JA3AJ86E36
P0421: Warmup Catalyst Efficiency Low (Bank 1). ... today with a P0421 warm up efficiency below threshold. previous shop replacd both 02s and the cat(all new aftermarket). while watching the pid data, the rear 02 seems to be real slow at idle. freeze frame shows the code was set while driving,closed loop,[....
October 08, 2008