Air-To-Air Aftercooler - An air-to-air aftercooler is a device that is used on turbocharged engines in order to cool inlet air that has undergone compression. The inlet air is cooled after the inlet air passes through the turbocharger. The inlet air is passed through an aftercooler (heat exchanger) that uses ambient air for cooling. The inlet air that has been cooled advances to the inlet manifold.
American Wire Gauge (AWG) - AWG is a measure of the diameter of electrical wire. AWG is also a measure of the current carrying capacity of electrical wire. When the AWG number is smaller, the diameter of the wire is larger. When the AWG number is larger, the diameter of the wire is smaller.
Before Top Center (BTC) - BTC is the 180 degrees of crankshaft rotation before the piston reaches the top center position in the normal direction of rotation.
Bypass Circuit - A bypass circuit is a circuit that is used as a substitute circuit for an existing circuit. A bypass circuit is typically used as a test circuit.
Coolant Temperature Sensor - The coolant temperature sensor measures the engine coolant temperature. The sensor sends a signal to the ECM. The engine's coolant temperature is used in Cold Mode operation. Coolant temperature is also used in order to optimize engine performance.
Code - See the Diagnostic Code.
Customer Specified Parameters - A customer specified parameter is a parameter that can be changed. A customer specified parameter's value is set by the customer. These parameters are protected by customer passwords.
CAT Data Link - The data link is an electrical connection that is used to communicate with other electronic devices that have microprocessors. The devices are compatible with the proposed American Trucking Association and the SAE Standard. These devices include trip recorders, electronic dashboards, and maintenance systems. The data link is also the communication medium that is used for programming with the electronic service tool. The data link is also used for troubleshooting with the electronic service tool.
Caterpillar Electronic Technician (Cat ET) - Cat ET is an electronic service tool. Cat ET is used for diagnosing a variety of electronic controls. Cat ET is also used for programming a variety of electronic controls.
Desired RPM - The desired rpm is input to the electronic governor within the ECM. The electronic governor uses the signal from the Accelerator Pedal Position Sensor, the Engine Speed Sensor, the Cruise Control, and the Customer Parameters in order to determine desired rpm.
Diagnostic Code - A diagnostic code is sometimes called a fault code. A diagnostic code is an indication of a problem or event in the electrical engine systems.
Diagnostic Lamp - A diagnostic lamp is sometimes called the check engine light. The diagnostic lamp is used to warn the operator of the presence of an active diagnostic code.
Direct Current (DC) - Direct current is the type of current that flows consistently in only one direction.
Duty Cycle - See Pulse Width Modulation.
Engine Control Module (ECM) - The ECM is the engine's control computer. The ECM provides power to the electronics. 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) - See Caterpillar Electronic Technician (Cat ET).
Estimated Dynamic Timing - Estimated dynamic timing is the estimate of the actual injection timing that is calculated by the ECM.
Enable Signal for the Exhaust Brake - The exhaust brake enable signal interfaces the ECM to the engine retarder. This prevents the operation of the exhaust brake under unsafe engine operating conditions.
Failure Mode Identifier (FMI) - The FMI describes the type of failure that was experienced by the component. The codes for the FMI were adopted from the standard practices of SAE (J1587 diagnostics).
Flash Memory - See the Personality Module.
Fuel Ratio Control (FRC) - The FRC is a limit that is based on the control of the fuel to air ratio. The FRC is used for emission control. When the ECM senses a higher turbocharger outlet pressure, the ECM increases the limit for the FRC in order to allow more fuel into the cylinders.
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 FRC, the rated position, and the actual engine speed.
Harness - The harness is the bundle of wiring that connects all the components of the electrical engine system.
Hertz (Hz) - Hz is the measure of frequency in cycles per second.
Inlet manifold temperature sensor - The inlet air temperature sensor is a sensor that measures the inlet air temperature. The sensor also sends a signal to the ECM.
Open Circuit - An open circuit is a broken electrical wire connection. The signal or the supply voltage cannot reach the intended destination.
Original Equipment Manufacturer (OEM) - An OEM is the manufacturer of a vehicle that utilizes a Caterpillar engine.
Parameter - A parameter is a programmable value which affects the characteristics or the behavior of the engine and/or vehicle.
Parameter Identifier (PID) - A PID is a numerical code that contains two digits or three digits. A numerical code is assigned to each component. The numerical code identifies data via the data link to the ECM.
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. The electrical engine systems require correct customer passwords in order to change customer specified parameters. The electrical engine systems require correct factory passwords in order to clear certain logged events. Factory passwords are also required in order to change certain engine specifications.
Personality Module - The personality module is the module in the ECM which contains all the instructions (software) for the ECM and performance maps for a specific horsepower family. Updates and rerates are accomplished by electronically flashing in new data. The updates and rerates are flashed in using Cat ET.
Power Take-Off (PTO) - The PTO is operated with the cruise control switches or dedicated inputs from the PTO. This mode of operation permits setting constant engine rpm when the vehicle is not moving or when the vehicle is moving at slow speeds.
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 Throttle Position Sensor.
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| Illustration 1 | g00284479 |
Example Of Pulse Width Modulation | |
Rated Fuel Position ("Rated Fuel Pos") - The rated fuel position indicates the maximum allowable fuel position (longest injection pulse). The rated fuel position will produce rated power for this engine configuration.
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.
Service Program Module (SPM) - The SPM is a software program on a computer chip that was programmed at the factory.
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 vehicle's frame.
Signal - A signal is a voltage or a wave that is used to transmit information that is typically from a sensor to the ECM.
Speed Burp - A speed burp is a sudden brief change in engine rpm.
Speed-timing Sensor - The speed-timing sensor is a sensor that provides a Pulse Width Modulated signal to the ECM. The ECM interprets this signal as the crankshaft position and the engine speed.
Subsystem - A subsystem is a part of the engine system that relates to a particular function.
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 the battery voltage of the vehicle that is supplied by the vehicle 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 sent from the accelerator pedal. This signal is interpreted by the ECM. The throttle position may be used as part of a power take-off control.
Total Tattletale - The total tattletale is the total number of changes to all system parameters.