Manifold Absolute Pressure Sensor

The Manifold Absolute Pressure (MAP) sensor, located at the top rear of the engine, on the intake plenum near the ignition coil assembly, responds to pressure changes in the intake manifold. See Fig 1 . The pressure changes occur based on the engine load. The MAP sensor has the following circuits:

• 5-volt reference circuit.
• Low reference circuit.
• MAP sensor signal circuit.

The Powertrain Control Module (PCM) supplies 5 volts to the MAP sensor on the 5-volt reference circuit. The PCM also provides a ground on the low reference circuit. The MAP sensor provides a signal to the PCM on the MAP sensor signal circuit which is relative to the pressure changes in the manifold. The PCM should detect a low signal voltage at a low MAP, such as during an idle or a deceleration. The PCM should detect a high signal voltage at a high MAP, such as the ignition in RUN position, engine OFF, or at a Wide Open Throttle (WOT). The MAP sensor is also used to determine the Barometric Pressure (BARO). This occurs when the ignition switch is turned to RUN position, engine OFF. The BARO reading may also be updated whenever the engine is operated at WOT. The PCM monitors the MAP sensor signal for voltage outside of the normal range.

Fig 1: Locating MAP Sensor (Century & Grand Prix Shown, Malibu Similar)

Courtesy of GENERAL MOTORS CORP.