3176 DIESEL TRUCK ENGINE Caterpillar

6.0 Glossary Of Terms

Usage:

After Market Device: As used here, a device or accessory installed by the customer or vehicle OEM after the engine is delivered.
Air-To-Air Aftercooler (ATAAC): A means of cooling intake air after the turbocharger, using ambient air for cooling. The intake air is passed through an aftercooler (heat exchanger) mounted in front of the radiator before going to the intake manifold.
Alternating Current (AC): The direction of current flow changes (alternates) regularly and constantly.
American Wire Gauge (AWG): A measure of the diameter (and therefor the current carrying ability) of electrical wire. The smaller the AWG number, the larger the wire.
Atmospheric Pressure Sensor: This sensor measures atmospheric air pressure and sends a signal to the ECM.
Before Top Dead Center (BTDC) or Before Top Center (BTC): The 180° of crankshaft rotation before the piston reaches Top Dead Center (normal direction of rotation).
Boost Pressure Sensor: This sensor measures inlet manifold air pressure and sends a signal to the ECM.
Bypass Circuit: A circuit, usually temporary, to substitute for an existing circuit, typically for test purposes.
Calibration: As used here, is an electronic adjustment of a sensor signal.
Caterpillar Engine Protection: The part of the Caterpillar Electronic Engine Control that monitors Coolant Temperature, Oil Pressure, and Coolant Level to flag the operator of detected problems. The Coolant Temperature and Oil Pressure Sensors are supplied by Caterpillar and monitored by the ECM. The Coolant Level Sensor is Vehicle OEM installed, but still monitored by the ECM. This is opposed to an After Market Engine Protection System which does not interface with the Caterpillar Electronic Engine Control.
Coolant Level Sensor: This OEM installed sensor detects the absence/presence of coolant at the probe and sends a signal to the ECM.
Cruise Control Range: The range that the cruise control can operate within. Usually limited to the speed range anticipated on the open road.
Code: See Diagnostic Code.
Coolant Temperature Sensor: This sensor detects the engine coolant temperature for Cold Mode operation and Caterpillar Engine Protection (if Engine Protection is not programmed OFF)
Customer Specified Parameter: A Parameter that can be changed and whose value is set by the customer. Protected by Customer Passwords.
Data Link: An electrical connection for communication with other microprocessor based devices that are compatible with the American Trucking Association and SAE Standard such as trip recorders, electronic dashboards, and maintenance systems. The Data Link is also the communication medium used for programming and troubleshooting with Caterpillar devices.
Desired RPM: An input to the electronic governor within the ECM. The electronic governor uses inputs from the Throttle Position Sensor, Engine Speed/Timing Sensor and Customer Parameters to determine "Desired RPM".
Desired Timing Advance ("Des Timing Adv" on ECAP): The injection timing advance calculated by the ECM as required to meet emission and performance specifications.
Diagnostic Code: Sometimes referred to as a "fault code", it is an indication of a problem or event in the 3176 System.
Diagnostic Lamp: Sometimes referred to as the "check engine light", it is used to warn the operator of the presence of an active diagnostic code.
Digital Diagnostic Tool (DDT): A Caterpillar electronic service tool used for programming and for diagnosing the 3176 system.
Direct Current (DC): The type of current where the direction of current flow is consistently in one direction only.
Dual Coil Vehicle Speed Sensor: A magnetic pickup that senses movement of the teeth on the output shaft of the transmission. It contains two coils, one to supply a signal to the vehicle speedometer, and one for the vehicle speed buffer.
Duty Cycle: See Pulse Width Modulation.
Electronic Control Analyzer Programmer (ECAP): An electronic service tool developed by Caterpillar used for programming and diagnosing a variety of Caterpillar electronic controls.
Electronic Control Module (ECM): The engine control computer that provides power to the 3176 electronics, monitors 3176 inputs and acts as a governor to control engine rpm.
Electronic Engine Control (3176): The complete electronic system that monitors and controls engine operation under all conditions.
Electronically Controlled Unit Injector: The injection pump which is mechanically actuated, electronically controlled unit injector combining the pumping, electronic fuel metering and injecting elements in a single unit.
Engine Speed/Timing Sensor: Provides a Pulse Width Modulated Signal to the ECM, which the ECM interprets as crankshaft position and engine speed.
Estimated Dynamic Timing: The ECM's estimation of actual injection timing.
Failure Mode Identifier (FMI): Type of failure the component experienced (adopted from SAE standard practice J1587 diagnostics).
0: Data valid but above normal operational range
1: Data valid but below normal operational range
2: Data erratic, intermittent, or incorrect
3: Voltage above normal or shorted high
4: Voltage below normal or shorted low
5: Current below normal or open circuit
6: Current above normal or grounded circuit
7: Mechanical system not responding properly
8: Abnormal frequency, pulse width, or period
9: Abnormal update
10: Abnormal rate of change
11: Failure mode not identifiable
12: Bad device or component
13: Uncalibrated device or component
14/15: Reserved for future assignment
Flash Code (FC): The Caterpillar proprietary code numbers which are ACTIVE are flashed out on the 3176 diagnostic lamp. The only numerical diagnostic code designation for 7LG1-7499 engines. For 7LG7500-UP engines it represents the code as it will be flashed out on the Diagnostic Lamp.
Fuel Ratio Control (FRC): FRC Fuel Pos. - is a limit based on control of the fuel-air ratio and is used for emissions control purposes. When the ECM senses a higher boost pressure (more air into cylinder), it increases the "FRC Fuel Pos" limit (allows more fuel into cylinder).
Fuel Position: An internal signal within the ECM, from the Electronic Governor to Fuel Injection Control. It is based on desired RPM, FRC Fuel Position, rated fuel position and engine RPM. Reference "3176 System Overview" in Section 1 of this manual.
Harness: The wiring bundle (loom) connecting all components of the 3176 System.
Hertz (Hz): Measure of frequency in cycles per second.
Inlet Air Temperature Sensor: This sensor detects the inlet manifold temperature. The ECM monitors the inlet air temperature and coolant temperature to adjust injection timing.
Oil Pressure Sensor: This sensor measure engine oil pressure and sends a signal to the ECM as part of Caterpillar Engine Protection.
Open Circuit: Condition where an electrical wire or connection is broken, so that the signal or the supply voltage can no longer reach its intended destination.
Original Equipment Manufacturer (OEM): As used here, the manufacturer of a vehicle in which a Caterpillar engine is installed.
Parameter: A programmable value which affects the characteristics or behavior of the engine and/or vehicle.
Password: A group of numeric or alpha-numeric characters, designed to restrict access to parameters. The 3176 System requires correct passwords in order to change Customer Specified Parameters (Customer Passwords) or certain engine specifications (Factory Passwords). Passwords are also required to clear certain diagnostic codes.
Pedal Mounted Throttle Position Sensor: This sensor measures pedal position and sends a signal to the ECM. The sensor is mounted on a throttle pedal assembly. See Remote Mounted Throttle Position Sensor.
Personality Module or Ratings Personality Module: The module attached to the side of the ECM which contains all the instructions (software) for the ECM and performance maps for a specific horsepower family.
Parameter Identifier (PID): Two or three digit code which is assigned to each component.
Programmable Electronic Engine Control (PEEC): The electronic control used on the Caterpillar 3406B/3406C engines. Not used or compatible with the 3176 engine.
Progressive Shifting: Shifting up through the lower gears quickly by not winding up the engine in each gear. Shifts are made above peak torque but below rated rpm. Needlessly winding up the engine into the higher rpm ranges before shifting to the next gear wastes fuel and fails to take advantage of the torque rise of the engine. The two steps (LoGr1, LoGr2) approximate ideal progressive shifting. Low gear #1 is typically set no lower than peak torque plus 200 rpm. Low gear #2 is typically set midway between Low gear #1 rpm limit and Top Engine Limit.
Power Take Off (PTO): Operated with the cruise control switches, this mode permits setting a constant engine rpm when the vehicle is not moving (lik a manual throttle control cable).
Pulse Width Modulation (PWM): A signal consisting of variable width pulses at fixed intervals, whose "TIME ON" versus "TIME OFF" can be varied (also referred to as "duty cycle").

Example of Pulse Width Modulation Signals
Rated Fuel Position: ("Rated Fuel Pos" on ECAP) - this indicates the maximum allowable fuel position (longest injection pulse). It will produce rated power for this engine configuration.
Reference Voltage: A regulated voltage supplied by the ECM to a sensor. The reference voltage is used by the sensor to generate a signal voltage.
Remote Mounted Throttle Position Sensor: This sensor measures pedal position and sends a signal to the ECM. The sensor is mounted off of the throttle pedal assembly, usually near the fire wall in the engine compartment (not the cab). The throttle pedal is connected through an adjustable linkage to this pedal. See Pedal Mounted Throttle Position Sensor.
Retarder Enable Signal: The retarder enable signal interfaces the ECM to the engine retarder. This will prohibit operation of the engine brake during undesirable engine operating conditions (such as while the engine is being fueled).
Sensor: A device used to detect and convert a change in pressure, temperature, or mechanical movement into an electrical signal.
Service Program Module: A software program on a factory programmable computer chip, designed to adapt an ECAP or DDT to a specific application.
Short Circuit: A condition where an electrical circuit is unintentionally connected to an undesirable point. Example: a wire which rubs against a vehicle frame until it wears off its insulation and makes electrical contact with the frame.
Signal: A voltage or waveform used to transmit information typically from a sensor to the ECM.
Speed "burp": A sudden brief change in engine speed.
Subsystem: As used here, it is a part of the 3176 System that relates to a particular function, for instance: throttle subsystem, etc.
Supply Voltage: A constant voltage supplied to a component to provide electrical power for its operation. It may be generated by the ECM, or it may be vehicle battery voltage supplied by the vehicle wiring.
"T" Harness: A test harness designed to permit normal circuit operation while measuring voltages, typically inserted between the two ends of a connector.
Throttle Position: The ECM's interpretation of the signal from the Throttle Position Sensor.
Throttle Position Sensor: An electronic sensor which is connected to the accelerator pedal and sends a Pulse Width Modulated signal to the ECM.
Total Tattletale: Total number of changes to all Customer Specified Parameters.
Transducer: A device which converts a mechanical signal to an electrical signal
Transducer Module: A sealed unit mounted mounted on one end of the ECM, which contains the Boost Pressure Sensor and Atmospheric Pressure Sensor (if equipped), and protective signal conditioning circuitry.
Vehicle Speed Buffer: A device used to condition and amplify the output of the vehicle speed sensor.
Vehicle Speed Sensor: An electromagnetic pickup that measures vehicle speed from the rotation of gear teeth in the drive train of the vehicle.
Warning Lamp: Used to warn the operator of the presence of a Caterpillar Engine Protection detected problem.