The MAP sensor's vacuum hose is loose and cracking. Technician A says this sensor measures air mass to establish the fuel injector's base pulse width. Technician B says this sensor measures changes in intake manifold pressure. Who is correct

Both A and B

Explanation:

The Engine's electronic Control Unit (ECU) gets the instantaneous manifold pressure data from the Manifold Absolute Pressure or MAP sensor which it uses to determine the air density such that the proper engine air mass flow rate is also determined, and from which the allowable fuel flow rate for optimum combustion is established

As such the MAP sensor measures the air mass to establish the fuel injector's base pulse width, which controls the fuel delivery. The MAP sensor also measures intake manifold which is related to the density of the air.