COMPUSHIFT II can use a MAP (Manifold Absolute Pressure) as part of the shift and pressure control system. This is most often useful with engines that use forced induction (turbocharging or supercharging).
If you are using an engine management system that includes a MAP, then you can use that existing sensor for COMPUSHIFT II. In that case, your MAP sensor is already grounded, and you should set the MAP Sensor Ground to Off. If you are using a MAP solely for COMPUSHIFT II, then you should set the MAP Sensor Ground to On.
MAP Sensor Ground