# Is there a reason to monitor calculated (not measured) OBDII mode $01 catalyst temperature values? My assumption is that on a 2 bank system, if both catalyst always read the exact same temperature, the values are calculated or inferred from other sensor inputs. My guinea pig is a 2005 Ford Explorer with a 4.0 liter. In OBDII mode$01, no matter the operating condition, both banks will mirror each other. I even went as far as disconnecting a spark plug wire from cylinder 4, and drove 60 mph to heat up the bank 2 converter. I know that curiosity killed the cat (pun intended), but I haven't found a use case for these values when they are calculated or inferred.

So since the catalyst temperature pid values remained equal during this test drive, why would a technician ever need to monitor them?