Illustration 1, Illustration 2 and Illustration 3 show the typical locations of the sensors for 3412E and C30 Marine Engines. Specific engines may appear different from the above illustrations due to differences in applications.
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| Illustration 1 | g00878139 |
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Top view (1) Connector for the oil pressure sensor in the marine transmission (2) Connector for the oil temperature sensor in the marine transmission (3) Injection actuation pressure control valve (4) Engine oil temperature sensor (5) Engine oil pressure sensor (6) Coolant level sensor (7) Secondary speed/timing sensor (8) Atmospheric pressure sensor (9) Fuel temperature sensor (10) Primary speed/timing sensor (11) Injection actuation pressure sensor (12) Coolant temperature sensor (13) Turbocharger outlet pressure sensor for 3412E Marine Engines (14) Turbocharger outlet pressure sensor for C30 Marine Engines (15) Inlet air temperature sensor for C30 Marine Engines | |
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| Illustration 2 | g00533536 |
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Right side engine service (14) Fuel pressure sensor | |
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| Illustration 3 | g00533578 |
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Left side engine service (14) Fuel pressure 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 the specification.
Atmospheric pressure sensor (8) 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 | |
Note: Coolant level sensor (6) is an optional feature.
Coolant level sensor (6) monitors the level of the engine coolant. The coolant level sensor is used to detect a condition when the coolant level is low. The coolant level sensor provides information to the ECM. The output from the ECM can indicate a low coolant level through a relay or a lamp. Coolant must be added to the cooling system in order to correct the condition.
The system can be programmed with one of the following options:
"ENABLED" - The system will monitor the input from the coolant level sensor. The system is programmed to this value when the engine is shipped by Caterpillar.
"DISABLED" - The system will not monitor the input from the coolant level sensor. All of the diagnostics that are associated with the coolant level sensor will be disabled.
See the Operation and Maintenance Manual, "Customer Specified Parameters" for more information about programmable options.
Failure of the Coolant Level Sensor
A failure of the coolant level sensor will not cause a shutdown of the engine or any horsepower change.
Coolant temperature sensor (12) monitors engine coolant temperature. This feature is used for all engine system diagnostics with outputs from the ECM. The output of the ECM can indicate a high coolant temperature through a relay or a lamp.
| Coolant Temperature Sensor | |
| Activation temperature for the high coolant temperature fault | |
| Activation temperature for the very high coolant temperature fault | |
Failure of the Coolant Temperature Sensor
The ECM will detect a 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 sensor will be disabled if a failure occurs. A failure of the coolant temperature sensor will not cause a shutdown of the engine or any horsepower change.
Engine oil pressure sensor (5) is an absolute pressure sensor that measures the engine oil pressure in the main oil gallery. The lack of oil pressure does not prevent the ECM from starting the engine. The ECM monitors the oil pressure(J2/8) after engine start-up. The ECM may display a low pressure alarm immediately after starting the engine. The diagnostic code will not be logged for the first 15 seconds after the engine start-up.
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| Illustration 4 | g02045073 |
The setpoint is dependent upon the engine speed. 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 speed. If the DERATE mode of the engine monitoring system is selected, the ECM will derate the engine power. The engine horsepower will be limited.
Failure of the Engine Oil Pressure Sensor
The ECM will detect failure of the engine oil pressure sensor. The diagnostic lamp warns the user about the status of the engine oil pressure sensor. The engine oil pressure related strategies will be disabled in the event of a failure of the engine oil pressure sensor. A failure of the engine oil pressure sensor will not cause a shutdown of the engine or any horsepower change.
Engine oil temperature sensor (4) monitors the temperature of the engine oil. The ECM uses the information from the engine oil temperature sensor in order to adjust the timing of the fuel injection and the pressure of the fuel injection. The engine oil temperature sensor is also used by the ECM in order to determine initiation of Cold Start Strategy.
| Engine Oil Temperature Sensor | |
| Operating range for the engine oil temperature sensor | |
The engine speed/timing sensors provide information to the Electronic Control Module (ECM) by generating pulse signals as the timing reference ring rotates past the sensor pickups. If the ECM does not receive a signal from primary speed/timing sensor (10), the "DIAGNOSTIC" lamp will indicate a diagnostic fault code which will be logged in the ECM memory.
If the ECM does not receive a signal from the primary speed/timing sensor, the ECM will read the signal from secondary speed/timing sensor (7). The ECM continually checks in order to determine if there is a signal from both sensors. If either sensor fails, the faulty sensor should be replaced.
Intermittent failure of the sensors will cause erratic engine control.
Fuel pressure sensor (14) 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 | |
Injection Actuation Pressure Sensor
Injection actuation pressure sensor (11) provides a signal of the injection actuation pressure to the ECM. The ECM modifies the current to the injection actuation pressure control valve (3) in order to control the injection actuation pressure. The desired actuation pressure is based on the following engine parameters: quantity of fuel, injection timing, engine speed and engine operating mode.
Marine Transmission Oil Pressure Sensor
Monitoring the marine transmission oil pressure is a programmable option. The ECM monitors marine transmission oil pressure with a sensor that is located on the high pressure side of the transmission. High marine transmission oil pressure is detected for diagnostics.
| Marine Transmission Oil Pressure Sensor | |
| Operating range of the marine transmission oil pressure sensor | |
The ECM will indicate high oil pressure through the diagnostic lamp, and the ECM will log a fault.
Note: The connector for the oil pressure sensor in marine transmission (1) is shown in the illustration. Follow the wire to the actual sensor location.
Marine Transmission Oil Temperature Sensor
The marine transmission oil temperature sensor measures the temperature of the oil in the marine transmission. The ECM uses the information from the sensor in order to diagnose a fault. The information is also used to warn the operator of excessive marine transmission oil temperature.
| Marine Transmission Oil Temperature Sensor | |
| Operating range of the marine transmission oil temperature sensor | |
The ECM will indicate high marine transmission oil temperature through the diagnostic lamp, and the ECM will log a fault.
Note: The connector for the oil temperature sensor in marine transmission (2) is shown in the illustration. Follow the wire to the actual sensor location.
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.
The output from the TPS is a constant frequency signal with a pulse width that varies with the throttle position. This output signal is referred to as a Pulse Width Modulated signal (PWM signal). The PWM signal is expressed as a percentage between 0 and 100 percent.
The TPS will produce a duty cycle between 5 and 10 percent at low idle and between 90 and 95 percent at high idle. The percent duty cycle is translated into a throttle position between 0 and 100 percent by the ECM.
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| Illustration 5 | g00708129 |
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Speed control with PWM input signal (1) A 5% deadband ensures that the engine will reach low idle and high idle. (2) If the engine enters this range, the engine drops to low idle and a fault is logged. (A) PWM input signal to ECM (Percent duty cycle) (B) Percent throttle position (C) 0% (Programmed low idle) (D) 100% (Programmed high idle) | |
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| Illustration 6 | g00708221 |
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Definition of PWM signal Percent Duty Cycle = H ÷ P × 100 (H) High portion of the signal (P) Period of the signal | |
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| Illustration 7 | g00708250 |
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Duty Cycle (H) High portion of signal (P) Period of signal (E) 10% Duty Cycle (F) 90% Duty Cycle | |
Requirements for the PWM Input Signal
The following criteria are required for the correct operations of a non-Caterpillar TPS.
Active pull up with protected output and active pull down with protected output
Stop for the sensor:
- Low stop: 7.5 ± 2.5 %
- High stop: 92.5 ± 2.5 %
Output frequency:
- Minimum of 300 Hz
- Nominal of 500 Hz
- Maximum of 700 Hz
High output voltage:
- Minimum of 4.5 VDC
- Maximum of 32 VDC
Low output voltage:
- Minimum of −0.3 VDC
- Maximum of 0.5 VDC
Sink current:
- −1.5 mA
Source current:
- -2.0 mA
- The sourcing driver must be capable of sinking 1.5 mA if the output voltage is less than 13.0 VDC.
Output linearity:
- ± 2.5 % duty cycle versus throttle position
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. Refer to Operation and Maintenance Manual, "Engine Synchronization" for more information.
Turbocharger Outlet Pressure Sensor
Turbocharger outlet pressure sensor (13) provides a signal which corresponds to boost to the ECM. The air/fuel ratio control utilizes the actual engine speed and the turbocharger outlet 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.
Failure of the Turbocharger Outlet Pressure Sensor
The ECM will detect failure of the turbocharger outlet pressure sensor. The operator will be warned of the problem through the diagnostic lamp. The strategies that are related to the boost will be disabled. Engine power will be severely reduced in the event of a failure of the turbocharger outlet pressure sensor. A failure of the turbocharger outlet pressure sensor will not cause a shutdown of the engine.
Inlet air temperature sensor (14) measures the temperature of the inlet air. The ECM monitors the signal of the inlet air temperature sensor. The output of the ECM can indicate a high inlet air temperature through a relay or a lamp.
Failure of the Inlet Air Temperature Sensor
Failure of the inlet air temperature will not cause a shutdown of the engine or any horsepower change.