The following sensors are analog sensors:
- Coolant temperature sensor
- Turbocharger outlet pressure sensor
- Turbocharger inlet pressure sensor
- Atmospheric pressure sensor
- Filtered engine oil pressure sensor
- Unfiltered engine oil pressure sensor
- Crankcase pressure sensor
Atmospheric Pressure Sensor - This sensor measures barometric pressure. The sensor sends the signal to the electronic control module (ECM) for use in engine control and in operation.
Automatic Engine Speed Control (AESC) - The AESC switch allows the ECM to reduce engine speed when the operator has not moved a hydraulic control for four seconds. The AESC switch is also used as a throttle backup switch.
Before Top Center (BTC) - The BTC position is the amount of crankshaft rotation before the piston reaches the Top Center in the normal direction of rotation.
Calibration - Calibration is an electronic adjustment of a sensor signal.
CAT Data Link - The data link is an electrical connection for communication with other onboard microprocessor based devices that use the data link. These devices include electronic transmissions, electronic dashboards and maintenance systems. The data link is also the medium for communication that is used for programming and troubleshooting with the electronic service tool.
CAT Data Link Flash - The CAT data link flash provides the capability to flash the software for the engine control with the CAT data Link.
Communication Adapter Tool - This tool provides a communication link between the ECM and the electronic service tool.
Coolant Flow Switch - The switch detects the flow of jacket water coolant . The switch sends a signal to the ECM when there is no flow and the engine is running. The ECM will send a signal to the machine monitoring system in order to warn the operator of the problem.
Coolant Temperature Sensor - This sensor measures the temperature of the jacket water coolant. The sensor sends the signal to the ECM. The engine's coolant temperature is used to determine cold mode operation. Coolant temperature is used to provide engine protection.
Crankcase Pressure Sensor - This sensor measures the crankcase pressure. The sensor sends the signal to the ECM. The information is used to warn the operator of high crankcase pressure.
Desired RPM - The desired RPM is input to the electronic governor within the ECM. The electronic governor uses the input from the throttle in order to determine the desired RPM.
Diagnostic Code - A diagnostic code is an indication of an electrical problem in the electronic control system.
Digital Sensors - Digital sensors produce a Pulse Width Modulation or a Duty Cycle signal. The digital sensors that are used are the Exhaust Temperature Sensor and the Engine Speed/Timing Sensor. The exhaust temperature sensor is powered from a 8.0 ± 0.5 VDC supply. The engine speed/timing sensor is powered from a 12.5 ± 1.0 VDC supply.
Direct Current (DC) - Direct current is the type of current that flows consistently in only one direction.
Duty Cycle - See Pulse Width Modulation.
Electronic Control Module (ECM) - The ECM is the engine's control computer. The ECM drives the electronic unit injectors. The ECM monitors data that is input from the engine's sensors. The ECM acts as a governor in order to control engine rpm.
Electronic Technician (ET) - The ET is a Caterpillar electronic service tool that is used for diagnosing and programming a variety of electronic controls.
Electronic Unit Injector (EUI) - The EUI is a mechanically actuated, electronically controlled unit injector. The EUI combines the pumping, electronic fuel metering, and injecting elements into a single unit.
Engine Demand Controlled Fan - Engine demand controlled fan is a system that uses hydraulic oil in order to power a drive motor. The drive motor is connected to the engine cooling fan. Fan speed is controlled by regulating the amount of hydraulic oil that flows to the fan drive motor. The regulation of oil flow is accomplished by a solenoid. The solenoid is controlled by the ECM. The ECM uses the coolant temperature sensor in order to determine the speed for the fan.
Engine Speed/Timing Sensor - This sensor provides a Pulse Width Modulated signal to the ECM. The ECM interprets this signal as the crankshaft position and the engine speed.
Exhaust Temperature Sensor - These sensors measure the exhaust temperature to the turbochargers. The sensor sends a signal to the ECM. The exhaust temperature is used in order to derate the engine. This is done in order to prevent further engine damage if a unacceptable temperature is reached.
Filtered Engine Oil Pressure Sensor - This sensor measures the engine's oil pressure out of the filters. The sensor sends the signal to the ECM.
Flash - This is a method of transferring software over the data link with an electronic service tool.
Fuel Air Ratio Control (FARC) - The FARC uses sensors in order to control the air/fuel ratio. The FARC maximizes engine response and controls smoke emissions.
Fuel Filter Differential Pressure Switch - The switch detects a restriction in the fuel filter. The switch sends a signal to the ECM if an unacceptable restriction is reached. The ECM will send a signal to the machine monitoring system in order to warn the operator of the problem.
Fuel Position - The fuel position is a signal within the ECM. The signal is from the electronic governor. The signal goes to the fuel injection control. The signal is based on the desired engine speed, the rated position, and engine speed.
Ground Level Shutdown Switch - The ground level shutdown switch allows engine shutdown while the machine operator is not inside the cab compartment. The ECM remains active and an electronic service tool can be used to communicate with the ECM while the ground level shutdown feature is active with the keyswitch ON.
Harness - The harness is the bundle of wiring that connects all the components of the EUI system.
Hydraulic Demand Controlled Fan - Hydraulic demand controlled fan is a system that uses hydraulic oil in order to power a drive motor. The drive motor is connected to the cooling fan for the hydraulic oil. Fan speed is controlled by regulating the amount of hydraulic oil that flows to the fan drive motor. The regulation of oil flow is accomplished by a solenoid. The solenoid is controlled by the ECM. The ECM uses the hydraulic oil temperature sensor in order to determine the speed for the fan.
Hydraulic Oil Temperature Sensor - The hydraulic oil temperature sensor measures the temperature of the hydraulic oil. The sensor sends a signal to the ECM. The temperature of the hydraulic oil is used to determine the correct fan speed for the demand controlled fan. The demand controlled fan protects the machine during high oil temperatures.
Injection Timing Control - Injection timing control is the use of the electronic unit injectors in order to provide total electronic control of the fuel injection timing.
Keyswitch Power - The ECM turns on when the ECM senses the battery voltage. The battery voltage is input by the keyswitch. When the voltage is removed, the ECM turns off.
Liquid Crystal Display (LCD) - The LCD is a part of the monitoring panel. The monitoring panel is used to display information to the operator about the condition of the machine systems and system diagnostic information.
Open Circuit - An open circuit is a broken electrical connection. The signal or the supply voltage cannot reach the intended destination.
Parameter - A parameter is a programmable value which affects the characteristics or the behavior of the engine and/or machine.
Password - A password is a group of numeric characters or alphanumeric characters. A password is designed to restrict the changing of information in the ECM.
Personality Module - A personality module refers to the software that is downloaded into the ECM. The module contains all the instructions (software) for the ECM and performance maps for a specific application.
Pulse Width Modulation (PWM) - A PWM is a digital type of electronic signal that corresponds to a measured variable. The length of the pulse (signal) is controlled by the measured variable. The variable is quantified by a certain ratio. This ratio is the percent of "on-time" that is divided by the percent of "off-time". A PWM signal is generated by the exhaust temperature sensor.
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| Illustration 1 | g00284479 |
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Example of pulse width modulation | |
Rated Fuel Limit - The rated fuel limit indicates the maximum allowable fuel position.
Reference Voltage - The reference voltage is a regulated voltage that is used by the sensor in order to generate a signal voltage.
Sensor - A sensor is used to detect a change in the pressure, in the temperature, or in mechanical movement. When any of these changes are detected, a sensor converts the change into an electrical signal.
"Serv Code" Indicator - This indicator is used to warn the operator of the presence of active diagnostics.
Short Circuit - A short circuit is an electrical circuit that is mistakenly connected to an undesirable point. For example, an electrical contact is made with the frame whenever an exposed wire rubs against a machine's frame.
Shutdown Switch - The shutdown switch disconnects power from the ECM.
Signal - A signal is a voltage or a wave that is used to transmit information that is typically from a sensor to the ECM.
Static Timing - Static timing is the basis for fuel injection timing and valve mechanism operation. Static timing is determined by the Timing Reference Ring and the alignment of the rear gear group and the camshaft timing pin.
Supply Voltage - Supply voltage is a constant voltage that is supplied to a component in order to provide electrical power for operation. Supply voltage may be generated by the ECM. Supply voltage may also be machine battery voltage that is supplied by the machine wiring.
"T" Harness - This harness is a test harness that is designed to permit normal circuit operation and the measurement of the voltage simultaneously. Typically, the harness is inserted between the two ends of a connector.
Throttle Position - The throttle position is the interpretation of the signal from the Throttle Position Sensor. The interpretation is made by the ECM.
Throttle Position Sensor - This sensor is an electronic digital sensor that is used to adjust the desired engine speed. The throttle position sensor sends a signal to the ECM.
Total Tattletale - The total tattletale is the total number of changes to all system parameters.
Turbocharger Compressor Inlet Pressure Sensor - This sensor measures the inlet air pressure in the tubes in the air induction system. The sensor sends signals to the ECM.
Turbocharger Compressor Outlet Pressure Sensor - This sensor measures the inlet manifold air pressure. The sensor sends a signal to the ECM.
Unfiltered Engine Oil Pressure Sensor - This sensor is used to determine low engine oil pressure.
User Defined Shutdown - This is a switch input into the ECM. The user defined shutdown allows the owner of the machine to install an aftermarket system. This system is used for engine shutdown. The ECM terminates the fuel injection when the switch input is connected to a ground.
Variable Speed Fan - The variable speed fan is a system that uses hydraulic oil in order to power a drive motor. The drive motor is connected to the engine cooling fan. Fan speed is controlled by regulating the amount of oil that flows to the fan drive motor. The regulation of oil flow is accomplished by a solenoid. The solenoid is controlled by the ECM. The ECM uses the coolant temperature sensor in order to determine the speed for the fan.
Vital Information Management System (VIMS) - The VIMS receives information from the control modules on the machine. The VIMS displays the information to the operator. The display shows system diagnostic information to the operator.