Circuit/System Description
WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The MAP sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. The engine control module (ECM) supplies 5 volts to the MAP sensor on a 5-volt reference circuit, and provides a ground on a low reference circuit. The MAP sensor provides a voltage signal to the ECM on a signal circuit relative to the intake manifold pressure changes.