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| Illustration 1 | g00659129 |
(1) Coolant temperature sensor (2) Inlet air temperature sensor (3) Boost pressure sensor (4) Fuel temperature sensor (5) Atmospheric pressure sensor (6) Oil pressure sensor | |
Atmospheric Pressure
The atmospheric pressure sensor is an absolute pressure sensor that measures crankcase pressure. The two pressures are calculated by subtracting the reading for the atmospheric pressure sensor. The atmospheric sensor measures pressure from 0 kPa (0 psi) to 116 kPa (17 psi). The atmospheric pressure sensor is supplied with 5 VDC by the ECM. Both the boost pressure and the oil pressure are communicated to the ECM. The service tools with the data link can retrieve the values.
Boost Pressure
The boost pressure sensor provides a signal which corresponds to boost to the ECM. The air/fuel ratio control utilizes the actual engine speed and the boost pressure sensor in order to control the transient smoke level. The ECM can control injection timing and the amount of fuel that is injected. When the throttle is increased and when the engine demands more fuel, the fuel limit is controlled in order to reduce overall smoke levels of the engine exhaust.
Coolant Temperature
The engine coolant temperature is measured by an electronic sensor that is mounted on the water outlet housing. The signal for the engine coolant temperature sensor is used to modify the engine fueling and the signal is used to modify the engine timing. By modifying the engine fueling and the engine timing, the engine will improve the following conditions: cold start capability and white smoke cleanup. The ECM supplies the coolant temperature sensor with 5.0 ± .5 VDC. The sensor output voltage is 0.5 to 4.5 VDC. The sensor output voltage depends on the engine coolant temperature. Coolant temperature is used in the Cold Mode Operation. Coolant temperature is also used for Engine Monitoring.
Engine Oil Pressure
The oil pressure sensor is an absolute pressure sensor that measures oil pressure in the oil gallery. The oil pressure is communicated over the data link and the oil pressure is displayed by the service tools. The ECM uses the sensor input only if the parameter for the Engine Monitoring is programmed to one of the following functions:
- Warning Mode
- Derate Mode
- Shutdown Mode
The oil pressure sensor measures pressure from 0 kPa (0 psi) to 690 kPa (100 psi). The sensor is supplied by the ECM with 5 VDC.
Fuel Temperature
The fuel temperature is monitored in order to adjust the calculations for the fuel rate. The fuel temperature is monitored for the power correction when the fuel temperatures exceed 30°C (86°F) in order to provide constant power. The value for the power correction for the maximum power is 70°C (158°F). Fuel temperature that exceeds 90°C (194°F) for ten minutes causes a diagnostic code to be logged.
Inlet Air Temperature
The sensor for the inlet air temperature measures the temperature of the air in the inlet manifold. The Electronic Control Module (ECM) monitors the sensor signal for the inlet air temperature. The output of the ECM can indicate high inlet air temperature through a relay or a lamp. The sensor for the inlet air temperature will not cause a shutdown of the engine or any horsepower change. Inlet air temperature is used in the cold mode operation.
Note: The sensor will be affected by the heat that is conducted from the air in the inlet manifold when the engine is idling, and after the engine is shut off. This warm-up is due to the lack of coolant circulation through the engine. The reading from the sensor for the inlet air temperature may be significantly higher than the actual temperature of the air inside the inlet manifold until the inlet manifold cools.