C32 Marine Engine Sensors and Electrical Components Caterpillar


Sensors and Electrical Components
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1.1. Sensor Locations
2.1. Failure of Sensors
3.2. All Sensors
4.1. Coolant Level Sensor
5.2. Failure of the Coolant Level Sensor
6.1. Coolant Temperature Sensor
7.2. Failure of the Coolant Temperature Sensor
8.1. Engine Oil Pressure Sensor
9.2. Low Oil Pressure Warning
10.2. Very Low Oil Pressure Warning
11.2. Failure of the Engine Oil Pressure Sensor
12.1. Engine Oil Temperature Sensor
13.1. Engine Speed/Timing Sensor
14.1. Fuel Temperature Sensor
15.1. Inlet Air Temperature Sensor
16.2. Failure of the Inlet Air Temperature Sensor
17.1. Marine Transmission Oil Pressure Sensor
18.1. Marine Transmission Oil Temperature Sensor
19.1. Turbocharger Outlet Pressure Sensor
20.2. Failure of the Turbocharger Outlet Pressure Sensor

Sensor Locations

The following illustrations show the typical locations of the sensors for C32 Marine Engines. Specific engines may appear different from the illustrations due to differences in applications.



Illustration 1g01137029
Front View
(1) Engine oil pressure sensor
(2) Coolant level sensor
(3) Secondary speed/timing sensor
(4) Primary speed/timing sensor


Illustration 2g01137056
View A-A
(5) Fuel pressure sensor
(6) Fuel temperature sensor


Illustration 3g01137058
Top View
(7) Inlet air pressure sensor
(8) Inlet air temperature sensor
(9) Coolant temperature sensor

Failure of Sensors

All Sensors

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 outside of the specification.

Coolant Level Sensor

Note: Coolant level sensor (7) is an optional feature.

The coolant level sensor 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 AVSpare.

"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

Coolant temperature sensor (9) 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.

Table 1
Coolant Temperature Sensor 
Activation temperature for the high coolant temperature fault  103°C (217°F) 
Activation temperature for the very high coolant temperature fault  106°C (229°F) 

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

Engine oil pressure sensor (4) is an absolute pressure sensor that measures the engine oil pressure in the main oil gallery. The engine oil pressure sensor detects engine oil pressure for diagnostic purposes. The engine oil pressure sensor sends a signal to the ECM.

Table 2
Engine Oil Pressure Sensor 
Operating range for the engine oil pressure sensor  0 to 690 kPa (0 to 100 psi) 

Low Oil Pressure Warning

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.

Very Low Oil Pressure Warning

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

Engine oil temperature sensor (3) 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.

Table 3
Engine Oil Temperature Sensor 
Operating range for the engine oil temperature sensor  −40 to 120°C (−40 to 258°F) 

Engine Speed/Timing 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 (6). 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 Temperature Sensor

Fuel temperature sensor (11) 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.

Table 4
Fuel Temperature Sensor 
Operating range of the fuel temperature sensor for activation of the power correction by the ECM  30 to 70°C (86 to 158°F) 

Inlet Air Temperature Sensor

Inlet air temperature sensor (1) 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.

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.

Table 5
Marine Transmission Oil Pressure Sensor 
Operating range of the marine transmission oil pressure sensor  0 to 2900 kPa (0 to 420 psi) 

The ECM will indicate high oil pressure through the diagnostic lamp, and the ECM will log a fault.

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.

Table 6
Marine Transmission Oil Temperature Sensor 
Operating range of the marine transmission oil temperature sensor  0 to 120°C (32 to 248°F) 

The ECM will indicate high marine transmission oil temperature through the diagnostic lamp, and the ECM will log a fault.

Turbocharger Outlet Pressure Sensor

Turbocharger outlet pressure sensor (8) 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.

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