SW1 L4-1.9L SOHC VIN 8 (1996)
Manifold Pressure/Vacuum Sensor: Description and Operation
The manifold absolute pressure (MAP) sensor is mounted on the intake manifold. The MAP sensor measures the intake manifold pressure. Engine
vacuum is related to engine load and RPM changes. A high vacuum signal indicates a low intake manifold pressure. A low vacuum signal indicates a
high intake manifold pressure. The higher the pressure signal, the greater the load being placed on the engine.
The MAP sensor voltage is scaled by the PCM to pressure (kPa or psi). A high pressure (atmospheric pressure) produces an output of 4.5-5.0 volts,
about 95-105 kPa (14-15 psi). A low pressure (engine vacuum) produces about 0.5-0.90 volts, about 37-50 kPa (5-7psi). The MAP sensor is also used to
calculate barometric pressure under certain conditions.
By monitoring the MAP sensor output voltage signal, the PCM determines the manifold pressure and can increase or decrease the injector On-time (or
pulse width). The PCM also uses the MAP sensor signal to help control fuel, ignition timing, canister purge duty cycle and EGR operation.
