My 2013 Ford taurus police interceptor 3.5 has had bank 1 Catalytic converter replaced has had both rear bank 1+2 oxygen Sensors replaced and a full diagnostic scan showing that there's nothing wrong with the systems cleared the code and 2 days later it was back.Please Scotty anything that you could help me with. THANKS P.McGrattan.
Who did the "full diagnostic scan" and where was it done? Something upstream of the CAT is causing the p0420 code, usually oil burning or an overly rich mixture. I would find an alternate, qualified independent mechanic to use a high end scanner to check for codes and go from there.
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