Circuit/System Description

The barometric pressure (BARO) sensor measures the pressure of the atmosphere. This pressure is affected by altitude and weather conditions. A diaphragm within the BARO sensor is displaced by the pressure changes that occur from varying altitudes and weather conditions. The sensor translates this diaphragm action into the voltage signal input that is used by the engine control module (ECM) for diagnostics, emissions control, and to calculate fuel delivery.

Changes in BARO due to weather are relatively small, while changes due to altitude are significant. Pressure can range from 56 kPa at an altitude of 4 267 meters (14,000 feet), to 104 kPa at or below sea level.

The sensor has the following circuits:

• An ECM supplied and regulated 5-volt reference circuit
• An ECM supplied ground for the low reference circuit
• A sensor signal circuit that supplies a voltage input to the ECM

The control module monitors the stability of the BARO sensor output by comparing successive samples. If the control module detects that the difference between the samples is more than a predetermined amount, DTC P2227 sets.