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.
Engine Coolant Pressure Sensor for the Outlet
A pressure switch is at the outlet for the engine jacket water. If the outlet pressure is too low, the control system will activate a shutdown.
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.
Engine Coolant Temperature Sensor
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.
Intake Manifold Air Temperature Sensor
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.
The engine oil pressure is measured before the oil filters and after the oil filters . 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.
The O2 sensor generates 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 to achieve the level of emissions that is desired. To observe the output value of the sensor, use Cat ET to view the O2 levels parameter.
There are three engine speed timing sensors for the engine:
- One is on the crankshaft flywheel housing.
- One is on the front housing at the left camshaft.
- One is on the front housing at the right camshaft.
The crankshaft sensor detects a hole in the face of the flywheel, to determine crankshaft position.
Timing wheels are mounted to the front of both camshafts.
The timing wheels have a special tooth pattern and are monitored by the cam sensors.
The engine performs a timing calibration automatically, during every startup, based on the speed/timing signals from the crankshaft and the camshafts.
The ECM utilizes all three sensors to determine the crankshaft position and engine speed to calculate the next desired ignition signal.
If any one of the three sensor signals are lost the ignition will be disabled.
The detonation sensors monitor the engine for mechanical vibrations. Each sensor monitors two cylinders. The sensor produces a voltage signal that is proportional to the engine detonation. This information is processed by the ECM to determine detonation levels. To eliminate detonation, the ECM retards the timing of the cylinder. If detonation continues, the 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.
Intake Manifold Pressure Sensor
The sensor for inlet manifold air pressure is connected to the air inlet manifold. The sensor monitors the absolute manifold air pressure. This pressure 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.
Fuel Valve Differential Pressure Sensor
The differential pressure sensor for fuel monitors fuel pressure between the aftercooler and the gas regulator. The sensor functions to activate either a "Low Gas Fuel Differential Pressure Alarm" or a "High Gas Fuel Differential Pressure Alarm".
The sensor functions to activate a pressure alarm and controls valve position.
Throttle Differential Pressure Sensor
The differential pressure sensor for air/fuel mixture monitors pressure between the aftercooler and the intake manifold.
The sensor functions to activate either a "Low Throttle Differential Pressure Alarm" or a "High Throttle Differential Pressure Alarm" and controls valve position.