The amount of intake air flow must be inputted to the ECM in order to determine the fuel injection quantity. The MAPS(Manifold Absolute Pressure) calculates the amount of air indirectly as measuring pressure inside of the intake manifold. This mechanism is called Speed-Density Type.

The MAPS transfers analog output signal which is proportional to the change of intake manifold pressure, then, with this signal and RPM, the ECM calculates the amount of intake air flow.

The MAPS is mounted on the intake manifold to measure the pressure inside of the intake manifold, and it consists of a piezo electric element and hybrid IC which amplifies output signal from the element. The piezo electric element is a sort of a diaphragm using piezo electric effect. One side of the diaphragm is surrounded with vacuum chamber while intake pressure is applied to the other side. Thus, signals are output by the transformation of diagphragm according to change of pressure inside of the intake manifold.