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| Illustration 1 | g02139498 |
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View of the left side of a typical C18 Marine Engine (1) Sensor for the fuel pressure (2) Sensor for the fuel outlet temperature (3) Secondary engine control module (ECM) (4) Sensor for the air inlet temperature (5) Boost pressure sensor (6) Primary ECM (7) Oil pressure sensor (8) Crankcase pressure sensor (9) Fuel pressure sensor (10) Aftercooler coolant pressure (sea water) | |
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| Illustration 2 | g02139500 |
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View of the right side of a typical C18 Marine Engine (11) Rear exhaust temperature sensor (12) Coolant temperature sensor (13) Unfiltered engine oil pressure sensor (14) Front exhaust 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 not within the specification.
The coolant temperature sensor monitors engine coolant temperature. The coolant temperature sensor is used by the engine system diagnostics with an output from the Electronic Control Module. 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 the 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. Strategies that are related to the coolant temperature will be disabled if a failure occurs. The failure of the coolant temperature sensor will not cause a shutdown of the engine or any horsepower change.
The engine oil pressure sensor 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 low oil pressure setpoint is dependent upon the engine rpm. If Derate mode 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 the 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.
The fuel pressure sensor 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 | |
The fuel temperature sensor 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 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.