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| Illustration 1 | g00281158 |
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(1) Oil pressure sensor
(2) Air temperature sensor for the inlet manifold (3) Air pressure sensor for the inlet manifold (4) Atmospheric pressure sensor (5) Coolant temperature sensor (6) Primary speed/timing sensor (7) Backup speed/timing sensor (8) Fuel pressure sensor (9) Fuel temperature sensor | |
A failure of any of the sensors may be caused by one of the following malfunctions:
- Sensor output is open.
- Sensor output is shorted to "- battery" or "+ battery".
- Measured reading of the sensor is out of specification.
Atmospheric pressure sensor (4) measures the atmospheric pressure in the crankcase. A signal is sent to the Electronic Control Module (ECM).
| Atmospheric Pressure Sensor | |
| Operating pressure range for the atmospheric pressure sensor | |
The coolant temperature sensor (5) monitors engine coolant temperature. This feature is used for engine system diagnostics with an output from the Electronic Control Module (ECM). The output of the ECM can indicate a high coolant temperature through a relay or a lamp. In addition, the sensor activates the cold start strategy which improves the startability of the engine.
The minimum coolant temperature that will activate the alarm is
Failure of the Coolant Temperature Sensor
If one of the following conditions exist, a failure of the coolant temperature sensor may have occurred:
- Sensor output is open.
- Sensor output is shorted to ground or supply.
- Measured reading of the coolant temperature is out of specification.
The ECM will detect the failure of the coolant temperature sensor. The diagnostic lamp will warn the operator about the status of the coolant temperature sensor. The coolant temperature related strategies will be disabled. The failure of the coolant temperature sensor will not cause a shutdown of the engine or any horsepower change.
The engine oil pressure sensor (1) can detect engine oil pressure for diagnostic purposes. The engine oil pressure sensor sends a signal to the Electronic Control Module (ECM).
The setpoint is dependent upon the engine rpm. The fault will be active and logged only if the engine has been running for more than 15 seconds.
The very low oil pressure setpoint is dependent upon the engine rpm. If the customer specified parameter is selected, the ECM will derate the engine power. The engine horsepower will be limited.
Failure of the Engine Oil Pressure Sensor
If one of the following conditions exist, a failure of the engine oil pressure sensor may have occurred:
- The engine oil pressure sensor is open.
- The engine oil pressure sensor is shorted to ground or supply.
- Measured reading of the oil pressure is out of specification.
The ECM will detect the failure of the engine oil pressure sensor. The diagnostic lamp warns the user about the status of the engine oil pressure sensor. The oil pressure related strategies will be disabled. The failure of the engine oil pressure sensor will not cause a shutdown of the engine or any horsepower change.
If the ECM does not receive a signal from engine speed/timing sensor (6) and (7), the "DIAGNOSTIC" lamp will indicate a diagnostic fault code which will be logged in the ECM memory.
Intermittent failure of the sensor will cause erratic engine control.
Fuel pressure sensor (8) monitors the fuel filter outlet pressure. Low fuel pressure or high fuel pressure will not cause a shutdown of the engine or any horsepower change. Fuel pressure that is outside of the normal range will affect the engine performance. If the fuel filter outlet pressure is low, the fuel filter may need to be replaced.
| Fuel Pressure Sensor | |
| Minimum allowable pressure of the fuel transfer pump at full load speed | |
| Minimum allowable pressure in the fuel manifold at full load speed | |
Fuel temperature sensor (9) monitors the fuel temperature. Fuel temperature is monitored in order to adjust the fuel rate so that the engine will deliver consistent power. The fuel temperature sensor can also be used to warn the operator of excessive fuel temperature. A high fuel temperature can adversely affect the engine performance.
| Fuel Temperature Sensor | |
| Operating range of the fuel temperature sensor for activation of the power correction by the ECM | |
Air Temperature Sensor for the Inlet Manifold
The air temperature sensor for the inlet manifold (2) measures the inlet manifold air temperature. The Electronic Control Module (ECM) monitors the signal from the air temperature sensor for the inlet manifold. The output of the ECM can indicate high inlet manifold air temperature through a relay or a lamp. The air temperature sensor for the inlet manifold will not cause a shutdown of the engine or any horsepower change.
Note: The air temperature sensor for the inlet manifold will be affected by the heat that is conducted from the inlet manifold. This is true 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 air temperature sensor for the inlet manifold may be significantly higher than the actual temperature of the air inside the inlet manifold until the inlet manifold cools.
Air Pressure Sensor for the Inlet Manifold
The air/fuel ratio control utilizes actual engine speed and actual boost pressure (inlet manifold air pressure) in order to control the transient smoke level. 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.
The Electronic Control Module (ECM) controls injection timing and the amount of fuel that is injected.
Note: The air pressure sensor for the inlet manifold (3) is located on the top right side of the engine. The sensor is located in front of the air pressure sensor for the inlet manifold.
The boost pressure is determined from the difference in pressure between the air pressure sensor for the inlet manifold and the atmospheric pressure sensor (crankcase pressure).
Failure of the Air Pressure Sensor for the Inlet Manifold
A failure of the air pressure sensor for the inlet manifold may have occurred if any of the following conditions are present:
- The output of the air pressure sensor for the inlet manifold is open.
- The output of the air pressure sensor for the inlet manifold is shorted to ground or to supply.
- The reading of the air pressure sensor for the inlet manifold is out of specification.
The ECM will detect the failure of the air pressure sensor for the inlet manifold. The operator will be warned of the problem through the diagnostic lamp. The strategies that are related to the boost will be disabled. The failure of the air pressure sensor for the inlet manifold will not cause a shutdown of the engine or any horsepower change.
The Throttle Position Sensor (TPS) sends a signal to the ECM. The signal from the TPS is required in order to govern engine speed. The signal from the TPS is used by the ECM in order to calculate the desired engine speed. The TPS is calibrated during the initial installation of the engine.
Note: The throttle position sensor is not shown in the illustration.
Failure of the Throttle Position Sensor
An intermittent failure in the TPS causes the engine speed to vary erratically. The ECM will perform the following process:
- The ECM will detect the failure of the TPS.
- The ECM will warn the operator of the failure through the diagnostic lamp.
- The ECM will set the desired engine speed to low idle.
If a TPS fails in a twin engine application, the operator can use a synchronization switch to transfer the throttle control to the second TPS. Both engines can then be controlled with the second throttle. If both throttle position sensors fail, the engine speed will be reduced to low idle.