Manifold Absolute Pressure Sensor (MAPS) is a speed-density type sensor and is installed on the surge tank. It senses absolute pressure of the intake manifold surge tank. The MAPS transfers the analog signal proportional to the pressure of the intake manifold during off idle operation to the PCM. PCM uses a Barometric Pressure Sensor (BPS) for idle calculations. Using the MAPS signal, the PCM calculates the intake air quantity and engine speed. The MAPS consists of a piezo-electric element and a hybrid IC amplifying the element output signal. The element is silicon diaphragm type and adapts pressure sensitive variable resistor effect of semi-conductor. Because 100% vacuum and the manifold pressure apply to both sides of the sensor respectively, this sensor can output an analog signal by using the silicon variation proportional to pressure change.