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P0421 Diagnostic Trouble Code Discussion for May 2011

Warmup Catalyst Efficiency Low (Bank 1)

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Trouble Ticket Help Requests for DTC P0421
Help Request Posted
2003 Mazda MPV EX 3.0L History Codes VIN: JM3LW28J93
P0421: Warmup Catalyst Efficiency Below Normal (Bank 1). Van failed emissions - current DTC P0421 & P0431. Read O2 sensor voltages with vehicle warm and voltages on all 4 sensors are all over the place - .03 to .930 and jumping all over the place. I picked the easy fruit on this one - connections, grounds, senso...
May 04, 2011