The sensors also enable the ECM 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 | g01249176 |
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Front view (1) Manifold air pressure sensor | |
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| Illustration 2 | g01249186 |
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Top view on the front of the engine (2) Manifold air temperature sensor (3) Engine coolant temperature (4) Pressure sensor for unfiltered oil (5) Pressure sensor for filtered oil (6) Engine coolant pressure sensor (outlet) (7) Engine oil temperature sensor | |
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| Illustration 3 | g01249187 |
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Left rear view (8) Oxygen sensor (if equipped) (9) Buffer for the oxygen sensor (if equipped) (10) Speed/timing sensor | |
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| Illustration 4 | g01389247 |
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Rear view (11) NOX sensor (if equipped) (12) Buffer for the NOX sensor (if equipped) | |
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| Illustration 5 | g01389923 |
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Right side view (13) Detonation sensor (14) Pressure switch for the engine's coolant (inlet) | |
Manifold air pressure sensor (1) - 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 control system 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.
Manifold air temperature sensor (2) - 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.
Engine coolant temperature sensor (3) - 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.
Oil pressure sensors (4) and (5) - The engine oil pressure is measured before the oil filters (4) and after the oil filters (5). 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.
Engine coolant pressure sensor (6) - A pressure switch is located at the outlet for the engine jacket water. If the outlet pressure is too low, the control system will activate a shutdown.
Engine oil temperature sensor (7) - 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.
Oxygen sensor (8) and oxygen buffer (9) - If the engine uses oxygen feedback in order to control the air/fuel ratio, the oxygen sensor and the oxygen buffer generate a signal that is proportional to the percent of oxygen in the exhaust manifold. The control system uses the signal to adjust the air/fuel ratio in order to achieve the level of emissions that is desired. To observe the output value of the sensor, use Cat ET to view the "Actual Oxygen" parameter.
Speed/timing sensor (10) - The engine speed/timing sensor is located on the rear end of the left camshaft. The engine speed/timing sensor is monitored in order to determine the position of the crankshaft and the engine rpm. The control system uses the position of the crankshaft to determine the ignition timing. To observe the engine speed in rpm, use Cat ET to view the "Engine Speed" parameter.
NOX sensor (11) and NOX buffer (12) - If the engine uses NOX feedback in order to control the air/fuel ratio, the NOX sensor and the NOX buffer generate a signal that is proportional to the percent of NOX in the exhaust manifold. The control system uses the signal to adjust the air/fuel ratio in order to achieve the level of emissions that is desired. To observe the output value of the sensor, use Cat ET to view the "Actual NOx" parameter.
Detonation sensors (13) - The detonation sensors monitor the engine for mechanical engine vibrations. Each sensor monitors each bank of cylinders. The sensor produces a voltage signal that is proportional to the engine detonation. If detonation occurs, the ECM retards the ignition timing in order to reduce detonation.
Pressure switch for the inlet of the coolant (14) - 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 the Caterpillar Electronic Technician (ET) to view the "Engine Coolant Pump Pressure" parameter.