3408 & 3412 HIGH PERFORMANCE MARINE ENGINES Caterpillar

6.0 Glossary Of Marine ECM Terms

Usage:

Actual Rack: The ECM's interpretation of the signal from the Rack Position Sensor which represents actual position of the rack, assuming the sensor signal is valid. If the rack controls are working properly, "Actual Rock" should follow "Desired Rack".
After Market Device: A device or accessory installed by the customer after the engine is delivered.
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.
Boost Pressure Sensor: This sensor measures inlet manifold air pressure and sends a signal to the ECM.
Brushless Torque Motor (BTM): Solenoid used to move fuel rack servo spool valve and timing advance spool valve.
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.
Coolant Level Sensor: The coolant level sensor operates as a coolant loss sensor indicating the presence/absence of coolant at the sensor probe tip.
Coolant Temperature Sensor: The coolant temperature sensor measures the temperature of the engine coolant. The ECM uses this information to set the mode of operation and to notify the operator of excessive engine temperature if the engine protection mode is not Off.
Code: See Diagnostic Code.
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 Rack Position ("Des Rack Pos" on ECAP): The rack position where the ECM wants to move the rack, based on the ECM governor trying to maintain "Desired RPM". "Desired Rack" will not go farther than the "FRC Rack" or "Rated Rack".
Desired Engine Speed: An input to the electronic governor within the ECM. The electronic governor uses inputs from the Throttle Position Sensor, Synchronization Status and Customer Parameters to determine "Desired RPM".
Diagnostic Code: Sometimes referred to as a "fault code", it is an indication of a problem or event in the ECM 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.
Direct Current: The type of current where the only direction of current flow is consistently in one direction only.
Duty Cycle: See Pulse Width Modulation.
Electronic Control Analyzer Programmer (ECAP): A Caterpillar Electronic Service Tool used for programming and diagnosing a variety of electronic controls.
Electronic Control Module (ECM): The engine control computer that provides power to the ECM electronics, monitors ECM inputs and acts as a governor to control engine rpm.
Engine Speed Sensor: A magnetic sensor that measures engine speed from the rotation of the flywheel.
Engine Synchronization (Power Link): To control PORT or STBD engines using a single throttle lever.
Failure Mode Identifier (FMI): Type of failure the component experienced (adopted from SAE standard practice J1587 diagnostics).
Fuel Ratio Control (FRC) Rack Position: FRC Fuel Pos. - is a limit based on control of the fuel-air ratio and is used for emission 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 Off and Fuel On: Refers to minimum fuel and maximum fuel positions of the fuel rack.
Harness: The wiring bundle connecting all components of the ECM System.
Hertz (Hz): Measure of frequency in cycles per second.
Oil Pressure Sensor: This sensor measure engine oil pressure and sends a signal to the ECM.
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 vessel 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 ECM 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.
Personality Module or Ratings Personality Module: The small blue module inserted into the ECM which contains all the instruction (software) for the ECM and performance maps for a specific power family.
Parameter Identifier (PID): Two or three digit code which is assigned to each component.
Power Link: See Engine Synchronization.
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

Throttle vs. Duty Cycle Relationship

Rated Rack Position: A limit on rack position which provides the specified power and torque curves. This value comes from maps programmed into the personality module at the factory.
Rack Position Sensor: A linear position sensor which follows movement of the rack assembly and sends an electrical signal to the ECM.
Rack Solenoid (BTM): A rotary proportional solenoid (also called a BTM) used to move the fuel rack servo spool valve.
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.
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 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 vessel 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.
Speed Sensor Magnetic Pick-Up (SSMPU): Speed sensor magnetic pick-up (SSMPU) is used to sense engine speed.
Subsystem: As used here, it is a part of the ECM 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 vessel 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 throttle lever 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.