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P0420 Diagnostic Trouble Code Discussion for January 2015

Catalyst Efficiency Below Normal (Bank 1)


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Trouble Ticket Help Requests for DTC P0420
Help Request Posted
2005 Buick Rendezvous CXL 3.4L MIL Lamp on VIN: 3G5DB03E45
P0420: Catalyst System Low Efficiency. ... rendevous that keeps setting the infamous P0420. We had this vehicle in before and I had replaced the cat converter (only has one, shared with both banks)Rear HO2S mirrors primary sensor just like it did before. It was fine after I initially replaced the c...
January 14, 2015
2006 Cadillac DTS 4.6L MIL Lamp on VIN: 1G6KD57Y76
P0420: Catalyst System Low Efficiency (Bank 1). Car came in with code P0420. Converter tested marginal so I replaced cat with a Walker Ultra and updated the computer with the latest software for false code P0420 setting. Ran bay test to run monitor and passed. Road tested vehicle while watching oxygen senso...
January 17, 2015