Manifold Absolute Pressure (MAP) Sensor

The MAP sensor is mounted on top of intake manifold, near right rear corner of engine compartment. Sensor monitors changes in intake manifold pressure (vacuum) which result from engine load and speed variations. The ECM uses this information to control fuel delivery and ignition timing.

As intake manifold pressure increases (vacuum drops), additional fuel is required by engine. The MAP sensor sends this information to ECM, and ECM increases injector pulse width (injector "on" time). As manifold pressure decreases (vacuum increases), pulse width decreases. MAP sensor voltage signal to the ECM will vary from .5-.9 volts at closed throttle (high vacuum/low pressure) to 4.5-5.0 volts at wide open throttle (low vacuum/high pressure).