The derating of the engine starts at a specific barometric pressure. The barometric pressure is equal to the atmospheric pressure of an elevation. The atmospheric pressure is specific for the engine and for the engine rating. The default settings that are programmed at the factory are listed in Table 1.
| Altitude | |
| Parameter | Default Setting |
| Derate setpoint | 2T specification |
| Security level | Required password |
| Derating per 305 m (1000 ft) |
3% |
| Maximum derating | 35% of the rated power |
If the barometric pressure is below the setpoint, a warning and a derating will occur. The continuous schedule of the derating is three percent per 1 kPa (.15 psi) of pressure below the setpoint. The maximum derating is 35 percent.
Input For The Atmospheric Pressure Circuit
Atmospheric pressure is monitored by the atmospheric pressure sensor. The sensor is located on the mounting for the ECM. A 5.0 ± 0.5 VDC supply voltage is provided by the ECM. The output of the atmospheric pressure sensor is a DC signal. The sensor's output voltage is 0.2 volts to 4.8 volts. The ECM interprets the output voltage as atmospheric pressure.