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P0420 Diagnostic Trouble Code Discussion for April 2014

Catalyst Efficiency Below Normal (Bank 1)

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Trouble Ticket Help Requests for DTC P0420
Help Request Posted
2000 Toyota 4Runner Limited 3.4L MIL Lamp on VIN: JT3HN87R6Y
P0420: Catalyst Efficiency Below Normal (Bank 1). death sentence on the cat.Want to better understand afr sensors and why the rear o2 sensor is showing the cat works. I start from cold,b1s2 o2 switches until operating temp then stays pretty steady around .5 v. MODE 6 READINGS are as followed...$01 cat monitor...
April 21, 2014