Grand AM L4-144 2.4L DOHC VIN T SFI (1997)
Manifold Pressure/Vacuum Sensor: Description and Operation
MAP Sensor
Description
Manifold Absolute Pressure (MAP) sensor measures the changes in the intake manifold pressure which result from engine load and speed changes,
and converts this measurement into a voltage output.
Operation
The PCM sends a 5 volt reference signal to the MAP sensor. As the manifold pressure changes, the electrical resistance of the sensor also changes.
By monitoring the sensor output voltage, the PCM can determine the manifold pressure. A higher pressure, low vacuum (high voltage) requires
more fuel, while a lower pressure, higher vacuum (low voltage) requires less fuel.
A closed throttle on when the engine is decelerating would produce a relatively low MAP output, while a wide open throttle would produce a high
output. Manifold absolute pressure is the opposite of what you would measure on a vacuum gage. When manifold pressure is high, vacuum is low.
The MAP sensor is also used to measure barometric pressure under certain conditions, which allows the PCM to automatically adjust for different
altitudes.
Circuit Faults
A high or low voltage fault in the MAP sensor circuit should set a DTC P0107 or DTC P0108. If the MAP sensor sends an intermittent zero
voltage signal to the PCM, a DTC P0106 will set.
