Manifold Pressure/Vacuum Sensor: Description and Operation

Voltage Versus Pressure Chart:

The MAP sensor is a potentiometer that is mounted on the intake manifold and measures the changes in intake manifold pressure due to engine speed and load changes. The PCM supplies a 5 volt reference signal and a ground to the MAP sensor and the sensor in turn sends a voltage signal to the PCM. As manifold pressure increases (vacuum decreases), the voltage signal increases and as manifold pressure decreases (vacuum increases), the voltage signal decreases. A high pressure signal will be close to 5 volts and a low pressure signal will be close to 0 volt.