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P0420 Diagnostic Trouble Code Discussion for October 2013

Catalyst Efficiency Below Normal (Bank 1)

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Trouble Ticket Help Requests for DTC P0420
Help Request Posted
2007 Chevrolet Silverado 1500 LTZ 5.3L MIL Lamp on VIN: 3GCEK13M27
P0420: Catalyst System Low Efficiency (Bank 1). ... p0420.they changed cat assy. code came back on.I got veichle with p0420 & p0430.cats tested cold.o2's switching/following fronts.checked,tune-up new.no vac.leaks,no exhaust leaks,02's in correct positions.f/press,ok.holds pressure.stft and long term fu...
October 07, 2013