3508B Engine for Caterpillar Built Machines Caterpillar

The electronic control module (ECM) automatically compensates for engine operation at elevations above 2275 m (7500 ft). The electronic control system derates the fuel delivery. The derate is a function of barometric pressure. The barometric pressure is sensed by the system's atmospheric pressure sensor. The engine is derated approximately two percent for every 305 m (1000 ft) above 2275 m (7500 ft). This derating is maximized at 20 percent at 5275 m (17300 ft).

If a diagnostic code is active for the atmospheric sensor, the ECM will use the data from the right turbocharger inlet pressure sensor in order to determine the altitude. If a diagnostic code for the right turbocharger inlet pressure sensor and the atmospheric sensor is active, the ECM will use the data from the left turbocharger inlet pressure sensor in order to determine the altitude. If a diagnostic code is active for all three sensors, the derate will be set at 30.75 percent.