Manifold Pressure/Vacuum Sensor: Description and Operation

The Manifold Absolute Pressure (MAP) sensor measures the changes in the intake manifold pressure that result from engine load and speed changes, and converts this measurement into a voltage output.

The PCM sends a 5 volt reference signal to the MAP sensor. As the manifold pressure changes, the electrical resistance of the sensor also changes. By monitoring the sensor output voltage, the PCM can determine the manifold pressure. A higher pressure, low vacuum, high voltage, requires more fuel, while a lower pressure, higher vacuum, low voltage, requires less fuel.

A closed throttle when the engine is decelerating produces a relatively low MAP output, while a Wide Open Throttle (WOT) produces a high output. Manifold absolute pressure is the OPPOSITE of what is measured on a vacuum gauge. When manifold pressure is high, vacuum is low. The MAP sensor is also used to measure barometric pressure under certain conditions, which allows the PCM to automatically adjust for different altitudes.

A high or low voltage fault in the MAP sensor circuit should set a DTC P0107 or DTC P0108.