Manifold Pressure/Vacuum Sensor: Description and Operation

The Manifold Absolute Pressure (MAP) sensor responds to changes in intake manifold pressure. The PCM supplies a 5 volt reference and ground for the MAP sensor. The MAP sensor circuit provides a signal to the PCM relative to pressure changes in the manifold. With the key ON, engine not running the MAP sensor signal voltage to the PCM varies between 1.5 to 2.5 volts. With the engine running, the MAP sensor voltage to the PCM varies from below 2 volts at idle (low manifold absolute pressure - high vacuum) to above 4 volts at wide-open throttle (high manifold absolute pressure - low vacuum).