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  1. 2006 DTS, P0420 Catalyst system efficiency below threshold

    Cadillac DTS Forum 2006 through 2011
    SO I was out for a drive and the check engine light came on. Turned out to be a P0420, and from doing reading 1.) Converter bad 2.) O2 Sensor bad 3.) PCM reprogram 4.) Exhaust leak. My assumption from the data is the o2 in bank 1, sensor 2 has gone bad because its staying at a pretty much...
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