The sensors also enable the modules to activate alarms, derates, and shutoffs in response to abnormal operation. The functions of the sensors are described below.
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| Illustration 1 | g01457398 |
Right side view (1) Detonation sensors (2) Jacket water temperature sensor (3) Inlet manifold air temperature sensor (4) Jacket water inlet pressure switch (5) Prelube pump pressure switch | |
Detonation sensors (1 and 14) - The detonation sensors monitor the engine for mechanical engine vibrations. Each sensor monitors two cylinders. The sensor produces a voltage signal that is proportional to the engine detonation. The master ECM monitors the detonation sensors on the left bank and the slave ECM monitors the detonation sensors on the right bank. This information is processed by each ECM in order to determine detonation levels. To eliminate detonation, the master ECM or the slave ECM retards the timing of the cylinder. If detonation continues, the master ECM will shut down the engine. To observe the value of the output of the sensors, use Cat ET to view the "Cylinder #X Detonation Level". The "X" is the number for the particular cylinder.
Jacket water temperature sensor (2) - The temperature sensor is located in the water temperature regulator housing. To monitor the coolant temperature, the element must be in contact with the coolant. Otherwise, the sensor will not function properly. A high coolant temperature will activate an alarm or a shutdown. A low coolant temperature will only activate an alarm. The trip points for the activation can be programmed with Cat ET. The engine can be restarted after a shutdown due to high engine coolant temperature. However, another shutdown will occur after one minute if the temperature remains high. To observe the value of the output of the sensor, use Cat ET to view the "Engine Coolant Temperature" parameter.
Inlet manifold air temperature sensor (3) - A sensor for monitoring the manifold air temperature is located in the inlet elbow for the number one cylinder head. Excessive manifold air temperature can activate an alarm or a shutdown during high load or low load operation. The trip points for activation can be programmed with Cat ET. To observe the value of the output of the sensor, use Cat ET to view the "Inlet Air Temperature" parameter.
Jacket water inlet pressure switch (4) - A pressure switch is located at the inlet for the engine jacket water. If the inlet pressure is too high, the switch will activate a shutdown. To observe the status of the switch, use Cat ET to view the "Engine Coolant Pump Pressure" parameter.
Prelube pump pressure switch (5) - The prelube pump pressure switch is used by the control in order to indicate that oil pressure is sufficient to start cranking the engine.
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| Illustration 2 | g01457401 |
Left side view (6) Pressure sensor for unfiltered oil (7) Pressure sensor for filtered oil (8) Jacket water outlet pressure sensor (9) Emergency stop button (10) Terminal box for the master ECM (11) Turbocharger compressor outlet pressure sensor (12) Inlet manifold pressure sensor (13) Engine oil temperature sensor (14) Detonation sensors (15) Solenoid for the Gas Shutoff Valve (GSOV) (16) Speed/timing sensor | |
Oil pressure sensors (6) and (7) - The engine oil pressure is measured before the oil filters (6) and after the oil filters (7). An alarm or a shutdown can be activated by any of the following occurrences: low filtered oil pressure, low oil filter differential pressure and high oil filter differential pressure. The trip point for the activation of a warning or a shutdown for oil filter differential pressure can be programmed with Cat ET. To observe the value of the output of the sensor, use Cat ET to view the "Engine Oil Pressure" or the "Unfiltered Engine Oil Pressure" parameter.
Jacket water outlet pressure sensor (8) - A pressure switch is located at the outlet for the engine jacket water. If the outlet pressure is too low, the master ECM will activate a shutdown.
Turbocharger compressor outlet pressure sensor (11) - The boost pressure that is developed by the turbochargers is measured at the outlet of the aftercooler. The master ECM uses the signal from the turbocharger compressor outlet pressure sensor to control the compressor bypass valve. To observe the output value of the sensor, use Cat ET to view the "Turbocharger Compressor Outlet Pressure" parameter.
Inlet manifold pressure sensor (12) - The sensor for inlet manifold air pressure is connected to the air inlet manifold. The sensor monitors the absolute manifold air pressure. This is the atmospheric pressure plus the gauge pressure. The information is used by the master ECM to calculate the air flow. To observe the output value of the sensor, use Cat ET to view the "Inlet Manifold Air Pressure (abs)" parameter.
Engine oil temperature sensor (13) - An oil temperature sensor measures the engine oil temperature. A high oil temperature will activate an alarm or a shutdown. The trip points can be programmed with Cat ET. To observe the output value of the sensor, use Cat ET to view the "Engine Oil Temperature" parameter.
Speed/timing sensor (16) - The engine speed/timing sensor is located on the rear end of the left camshaft. Both the master ECM and the slave ECM monitor the engine speed/timing sensor in order to determine the position of the crankshaft and the engine rpm. With the position of the crankshaft, each ECM is able to determine the ignition timing. To observe the engine speed in rpm, use Cat ET to view the "Engine Speed" parameter.
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| Illustration 3 | g01457413 |
Rear view (17) NOX sensor group | |
NOX Sensor (17) - The NOX sensor indicates the concentration of NOX in parts per million (PPM) for the engine's exhaust. Power for the sensor is provided by the ECM. The sensor is activated after the conditions for a dew point strategy have been met. The conditions for the dew point strategy are based on engine speed and engine load. The ECM communicates with the sensor by a CAN data link. The CAN data link is used to activate the sensor when the dew point strategy has been satisfied. The Caterpillar Electronic Technician (ET) can be used to program the following parameters: "Desired NOx level setting", "NOx sensor calibration slope" and "NOx sensor calibration offset". Cat ET can be used to monitor the "Desired NOx level" and the "Sensor NOx level".
NOX sensor buffer (17) - The sensor buffer is used to process the measurements that are received from the sensor. The buffer transmits these measurements to the ECM via the CAN data link. The buffer also reports diagnostic data to the ECM over the CAN data link. The sensor buffer requires 16 to 36 volts in order to operate.
Note: The sensor and the sensor buffer are integrated parts. The sensor and the sensor buffer must be replaced as a single component, if necessary.