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P0420 Diagnostic Trouble Code Discussion for February 2012

Catalyst Efficiency Below Normal (Bank 1)

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Trouble Ticket Help Requests for DTC P0420
Help Request Posted
2005 Chevrolet Trailblazer LS 4.2L MIL Lamp on VIN: 1GNDT13SX5
P0420: Catalyst System Low Efficiency (Bank 1). ... engine light on. Customer wanted it checked out because she was thinking of buying it. The person selling it said nobody could figure out why the light was on. It had a code P0455. I commanded The vent valve on and off with my scanner and I could hear it c...
February 10, 2012
2006 Chevrolet Colorado LT 3.5L Poor Idle Quality, Hesitation, Stall, MIL Lamp on VIN: 1GCDS13626
P0420: Catalyst System Low Efficiency. This vehicle drives normally for about 30 seconds and then starts to bog down severely. MAF readings seem like they should be higher. If you "get on it", the MIL lamp will flash, however STFT doesn't move from 0.00. and the dash readout says "Reduc...
February 16, 2012
2005 Chevrolet Uplander LS 3.5L MIL Lamp on VIN: 1GNDX33165
P0420: Catalyst System Low Efficiency. After a few weeks of driving the SES will set 420 as a Catalyst System Low Efficiency. I have checked back preshure (ok) and inspected with frontside of converter with bore scope (no problem). While watching the upstream and downstream O2s together the upstrea...
February 17, 2012