Computer Command Control - Port Fuel Injection

Manifold Absolute Pressure (MAP) Sensor:

PURPOSE
The Manifold Absolute Pressure (MAP) sensor measures changes in the intake manifold pressure resulting from engine load and speed changes. The control module uses this information, compared with information from other sensors, to help determine to the amount of fuel required.

OPERATION
The computer sends a 5.0 volt reference signal to the MAP sensor. As pressure changes in the intake manifold occur, the electrical resistance of the MAP sensor also changes. By monitoring the sensor output voltage, the computer can determine the manifold absolute pressure. The lower the engine vacuum (high absolute pressure), the higher the MAP voltage output, indicating greater demand for fuel. The higher the engine vacuum, the lower the MAP voltage output, indicating less demand for fuel. Under certain conditions (key "ON" engine not running), the MAP sensor is also used to measure barometric pressure. This allows the computer to automatically adjust for different altitudes. The computer uses the MAP sensor to control fuel delivery and ignition timing.