When you monitor Fuel System Status on your vehicle you will see separate results for systems A & B.

These two values should not be mistaken for cylinder banks, but instead refer to two distinct fuel systems -  for example a truck that runs both diesel & LPG.

The majority of passenger vehicles will only have one fuel system, in this case the vehicle will typically display 'System B' as 'Open Loop'. In most cases, if your vehicle is operating normally and you see 'System B' open this just means the value is unused, and there's nothing to worry about.