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 provides a signal to the PCM relative to pressure changes in the manifold. The MAP sensor signal voltage to the PCM varies from between 1 volt at idle (low manifold absolute pressure - high vacuum) to above 4 volts with the key ON, engine not running or at wide-open throttle (high manifold absolute pressure - low vacuum).