About 6 months ago I had a pending P0420 code that I cleared and it never came back, I was convinced that the code was due to me stupidly adding a can of what turned out to be 2 cycle mixed fuel to the tank a week before the code appeared. Today I connected one of those cheap ELM327 scanners to the ODB port and the catalyst readings look a bit odd. OS2 sensor reading looks reasonable however the voltage is higher than the OS1? There are no codes (pending, stored or current) and all the monitors are set.