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P0420 Diagnostic Trouble Code Discussion for September 2004

Catalyst Efficiency Below Normal (Bank 1)

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Trouble Ticket Help Requests for DTC P0420
Help Request Posted
2000 Toyota 4Runner SR5 3.4L MIL Lamp on VIN: JT3HN86ROY
P0420: Catalyst Efficiency Below Normal (Bank 1). Problem . After several hundred miles of driving the Po420 code re-sets. The fuel trim at the time of the code setting is good. The vehicle is running at 45 mph with 25% load when the code was set. The cats that were put on were after market 3 way cats. They...
September 07, 2004