It‘s a 2000 B4C Chevy Camaro used police car with a LS1/auto trans. Today at a stop light the SES light went on. I went to Advance auto parts and found it said: Check engine code PO420: Catalyst System Efficiency below threshold (bank 1). I reset it and drove the car 2 miles and it didn‘t come back onI just bought the car and put premuim fuel in it and I am not sure if that would cause it or that it was less than a quarter tank of gas left.Anybody know what would cause that?
