The MAP or manifold absolute pressure sensor is used in a fuel injected motor to monitor the manifold pressure at all times of engine operation. The MAP sensor transmits data to the Engine Control Unit - ECM for optimum engine performance. This manifold absolute pressure sensor is just one of the many different sensors used in today's modern diesel engines.
The MAP or Manifold Absolute Pressure sensor has 5-volt reference and ground inputs and in turn, outputs a voltage signal between 0 and 5 volts depending on the pressure it senses. This sensor is responsible for measuring the pressure in the intake manifold about atmospheric pressure. When the pressure it senses is lower than atmospheric pressure (vacuum), the sensor will output a lower voltage. As the pressure it senses rises to match atmospheric pressure (vacuum drops), the voltage output of this sensor rises. This sensor also doubles as a barometric pressure sensor. When you turn the key on before starting the engine, the ECM takes the reading from the MAP sensor and uses that to calculate barometric pressure. The ECM uses barometric pressure as the basis for calculating fuel and spark delivery to the engine.
Please see the other Automotive Engine Sensors offered by KLM Performance inc.