Altitude Compensator: Description and Operation

Fig. 27 Barometric pressure sensor system diagram:

To comply with applicable emission control requirements at all altitudes vehicles equipped with fuel injection include a pressure sensor, Fig. 27 which is used as a high altitude compensator.

When the ignition switch is turned on and periodical thereafter the ECU monitors the pressure sensor to detect ambient barometric pressure. Fuel delivery time is then adjusted by the ECU to achieve the proper fuel/air ratio at any given altitude.