Manifold Pressure/Vacuum Sensor: Description and Operation

Map Sensor:

DESCRIPTION
The Manifold Absolute Pressure (MAP) Sensor is mounted in the upper intake manifold down stream of the throttle body and measures the changes in intake manifold pressure which result from engine speed and load changes. The Powertrain Control Module (PCM) supplies a 5 volt reference signal and a ground to the sensor and the sensor outputs another voltage signal that is proportional to the pressure signal. A high pressure (low vacuum) will produce a signal close to 5 volts and a low pressure (high vacuum) will produce a signal under one volt. The PCM scales the MAP sensor signal in kilo-Pascals (kPa). The MAP signal is the INVERSE of what is read on a vacuum gauge. When the MAP value is high, intake vacuum with a vacuum gauge will be low.

The PCM uses MAP information in conjunction with Intake Air Temperature (IAT) information to determine the density of air entering the engine. MAP information is also used to determine barometric pressure and for ignition control. A faulty MAP sensor may cause various driveability conditions and should set a Diagnostic Trouble Code.