Manifold Pressure/Vacuum Sensor: Description and Operation

Map Sensor:

Sensor Wiring Diagram:

The Manifold Absolute Pressure (MAP) sensor measures the changes in intake manifold pressure which results from engine load and speed changes. The sensor converts a pressure input to a voltage output. The MAP sensor output voltage signal is directly related to pressure (kPa). A high pressure (atmospheric pressure) will produce an output of about 4.5 to 5.0 volts. A low pressure will produce about 0.5 to 0.9 volts. Manifold absolute pressure is the opposite of what you would measure with a vacuum gauge. When manifold pressure is high, vacuum is low.



The MAP sensor is also used to calculate barometric pressure under certain vehicle conditions. This eliminates the need for a separate Barometric (BARO) sensor. As the manifold pressure changes, the electrical output of the sensor also changes. A higher pressure (low vacuum) requires more fuel, while a lower pressure (higher vacuum) requires less fuel. By monitoring the sensor output voltage, the PCM/ECM can calculate the manifold pressure, and increase or decrease the injector duration to allow for the addition or reduction of fuel. The PCM/ECM also uses the MAP sensor to control ignition timing. A failure in the MAP sensor circuit should set a code E031, E032, or E034.