Barometric Pressure Sensor: Description and Operation

Fig. 7 Altitude Sensor:

In areas of high altitude the air pressure is lower than at sea level. This results in the air being "thinner" or less dense, which means the engine will have less oxygen to burn. Depending on altitude, the amount of fuel is changed based on a signal from the altitude correction sensor. With the ignition switched ON or with the engine running, the altitude correction sensor will receive a constant voltage signal (approx. 8 volts) from the CIS-E control unit. With increasing altitude (decreasing air pressure), the air/fuel mixture will be adapted to the altitude by a reduction of current to the electro-hydraulic actuator. Thus, less fuel is injected at the cylinders. This function is deleted if the ECU is in "Limp Home" mode.