help: MAP sensor wiring

[GrandPrix34]

On the MAP sensor, there are 3 wires:

 

A(Black)

B(LtGreen)

C(Grey)

 

Does anyone know the leads they follow? I know the green wire is to the ECM as the MAP SIGNAL on A29...so which of the other 2 wires is the ground wire? ON the diagram it says C (grey) wire goes to the Throttle Position Sensor "A" wire and then into the ECM's 5V REF SENSOR connection...is that the 5V power source for the TP and MAP sensor?

 

So I would assume that the A wire "Black" leads to ground? On the diagram it leads to the A connection on the IAT sensor and the A connection on the A/C PRESSURE SENSOR and then leads into the ECM to the "REFERENCE LOW FOR IAT,MAP, AND A/C PRESS. SENSOR input.....is this the grounding wire for all 3 sensors??