C-12 TRUCK ENGINE Caterpillar

PB-10: Inspecting Electrical Connectors

System Operation

Figure PB-10.2 ECM Connectors

Figure PB-10.3: Connectors

Figure PB-10.4: Harness Routing And Plug Insertion

Functional Test

Figure PB-10.5: Connector Seals

Figure PB-10.6: Connector Pin Retention

PB-11: Ignition Key Switch And Battery Supply Circuits Test

System Operation

Figure PB-11.2: ECM Battery Circuit Schematic

Figure PB-11.3: ECM Terminal Locations

Diagnostic Codes

Functional Test

Figure PB-11.4: Breakout T Connector

Figure PB-11.5: Service Tool Bypass Harness

PB-12: Accelerator Pedal (Throttle) Position Sensor Circuit Test

System Operation

Figure PB-12.2: Cab Accelerator Pedal Position Sensor Schematic

Figure PB-12.3: Remote Accelerator Position Sensor Schematic

Figure PB-12.4: ECM Terminal Locations

Diagnostic Codes

Functional Test

Figure PB-12.5: Accelerator Pedal Assembly

PB-13: Lamp Circuit Test (Check Engine Lamp, Warning Lamp, or PTO Switch ON Lamp)

System Operation

Figure PB-13.2: Lamp Schematic

Figure PB-13.3: ECM Terminal Locations

Functional Test

Figure PB-13.4: Vehicle Harness Connector P1

Figure PB-13.5: Breakout T Connector

Figure PB-13.6: Breakout T Connector

Figure PB-13.7: Breakout T Connector

PB-14: Vehicle Speed Circuit Test

System Operation

Figure PB-14.2: Single Coil Speed Sensor, ECM Driven Speedometer Schematic

Figure PB-14.3: Single Coil Speed Sensor, Second Single Coil Sensor For Speedometer Schematic

Figure PB-14.4: Single Coil Speed Sensor, Data Link Driven Speedometer Schematic

Figure PB-14.5: Electronic Vehicle Speed Source, ECM Driven Speedometer Schematic

Figure PB-14.6: Electronic Vehicle Speed Source And Speedometer Schematic

Figure PB-14.7: ECM Terminal Locations

Diagnostic Codes

Functional Test

Figure PB-14.8: Vehicle Harness Connector P1

Figure PB-14.9: Breakout T Jumper Wires

Vehicle Speed Circuit Calibration

System Operation

Functional Test

PB-15: Cruise Control, Service Brake Pedal Position Switch #1 And Clutch Pedal Position Switch Circuit Test

System Operation

Figure PB-15.2: Cruise Control Kickout Status Screen Table

Figure PB-15.3: Idle Kickout Status Screen Table

Figure PB-15.4: Cruise Control, Service Brake Pedal Position Switch #1 And Clutch Pedal Position Switch Schematic

Figure PB-15.5: ECM Terminal Locations

Diagnostic Codes

Functional Test

Figure PB-15.6: Switch Or Pedal Position Status Results Table

Figure PB-15.7: Switch Jumper Position Status Results Table

Figure PB-15.8: Switch Jumper Position Status Results Table

Figure PB-15.11: Switch Jumper Position Status Results Table

PB-16: PTO Switch Circuit Test

System Operation

Figure PB-16.2: PTO Kickout Status Screen Table

Figure PB-16.3: PTO Configuration Cab Switches Schematic

Figure PB-16.4: PTO Configuration Remote Switches Schematic

Figure PB-16.5: PTO Configuration Remote Throttle Schematic

Figure PB-16.6: ECM Terminal Locations

Functional Test

Figure PB-16.7: Breakout T Connector

Figure PB-16.8: Breakout T Connector

Figure PB-16.9: Breakout T Connector

PB-17: Service Brake Pedal Position Switch #2 And Transmission Neutral Switch Circuits Test

System Operation

Figure PB-17.2: Service Brake Pedal Position Switch #2 Schematic

Figure PB-17.3: Transmission Neutral Switch Schematic

Figure PB-17.4: ECM Terminal Locations

Diagnostic Codes

Functional Test

Figure PB-17.5: Breakout T Connector

PB-18: Retarder Solenoid Circuits Test

System Operation

Figure PB-18.2: Retarder Schematic

Figure PB-18.3: ECM Pin Locations

Diagnostic Codes

Functional Test

PB-19: Idle Shutdown Timer And PTO Shutdown Timer Test

System Operation

Diagnostic Codes

Functional Test

PB-20: Tachometer Circuit Test

System Operation

Figure PB-20.2: Tachometer Schematic 1

Figure PB-20.3: Tachometer Schematic 2

Figure PB-20.4: ECM Terminal Locations

Functional Test

Figure PB-20.5: Breakout T Connector

PB-21: SAE J1587/1708 (ATA) Data Link Circuit Test

System Operation

Figure PB-21.2: ATA Data Link Schematic

Figure PB-21.3: ECM Terminal Locations

Functional Test

Figure PB-21.4: ATA Data Link Connectors

Figure PB-21.5: Breakout T And ECM Connector P1

Figure PB-21.6: Service Tool Bypass Harness

PB-22: Cooling Fan And A/C High Pressure Switch Circuits Test

System Operation

Figure PB-22.4: On-Off Fan With A/C High Pressure Switch Connected To ECM, And Direct Solenoid Connection

Figure PB-22.5: On-Off Fan With A/C High Pressure Switch Not Connected To ECM, And Direct Solenoid Connection

Figure PB-22.6: On-Off Fan With A/C Control Unit Connected To ECM, And Direct Solenoid Connection

Figure PB-22.7: On-Off Fan With A/C High Pressure Switch Not Connected To ECM, And Normally Closed Relay Connection

Figure PB-22.8: On-Off Fan With A/C High Pressure Switch Connected To ECM, And Normally Open Relay Connection

Figure PB-22.9: On-Off Fan With A/C High Pressure Switch Not Connected To ECM, And Normally Open Relay Connection

Figure PB-22.10: On-Off Fan With A/C High Pressure Switch Connected To ECM, And Normally Closed Relay Connection

Figure PB-22.11: Three Speed Fan With Direct Solenoid Connection

Figure PB-22.12: ECM Terminal Locations

Functional Test

Figure PB-22.13: Breakout T Connector

Figure PB-22.14: Breakout T Connector

PB-23: Coolant Level Sensor Circuit Test

System Operation

Figure PB-23.2: 4-Pin Coolant Level Sensor Schematic

Figure PB-23.3: ECM Terminal Locations

Diagnostic Codes

Functional Test

Figure PB-23.4: Jumper Wire

Figure PB-23.5: Breakout T Connector

Figure PB-23.6: Jumper Wire

Figure PB-23.7: Breakout T Connector

PB-24: Powertrain Data Link Circuit Test

System Operation

Figure PB-24.2: Data Link Connections

Figure PB-24.3: Data Link Connections

Figure PB-24.4: ECM Pin Locations

Diagnostic Codes

Functional Test

Figure PB-24.5: Electronic Service Tool Status Screen Definition Table

Figure PB-24.6: Electronic Service Tool Powertrain Datalink Screen

PB-25: Eaton Top 2 Transmission Circuit Test

System Operation

Figure PB-25.2: Eaton Top 2 Transmission Schematic

Figure PB-25.3: ECM Pin Locations

Diagnostic Codes

Functional Test

PB-26: Output Selections Circuit Test (Auxiliary Brake, Engine Running, Engine Shutdown, and Starting Aid Output)

System Operation

Figure PB-26.2: Auxiliary Brake Relay Circuit

Figure PB-26.3: Engine Running Output Circuit

Figure PB-26.4: Engine Shutdown Output Circuit

Figure PB-26.5: Starting Aid Output Circuit

Figure PB-26.6 ECM Terminal Locations

Functional Test

PB-27: Input Selections Switch Circuit Test (Fan Override, Ignore/Brake Clutch, Torque Limit, Diagnostic Enable, PTO Engine RPM Set Speed Input A, PTO Engine RPM Set Speed Input B, Starting Aid On/Off and Two Speed Axle Switch)

System Operation

Figure PB-27.1: Fan Override Switch Schematic

Figure PB-27.2: Ignore Brake/Clutch Switch Schematic

Figure PB-27.3: Torque Limit Switch Schematic

Figure PB-27.4: Diagnostic Enable Switch Schematic

Figure PB-27.5: PTO Engine RPM Set Speed Input A Switch Schematic

Figure PB-27.6: PTO Engine RPM Set Speed Input B Switch Schematic

Figure PB-27.7: Starting Aid On/Off Switch Schematic

Figure PB-27.8: Two Speed Axle Switch Schematic

Figure PB-27.9: ECM Terminal Locations

Functional Test

Figure PB-27.10: Breakout T Connector

PC-30: ECM Memory Test

System Operation

Diagnostic Codes

Functional Test

PC-31: Engine Speed/Timing Circuit Test

System Operation

Figure PC-31.2: Speed/Timing Sensors Schematic

Figure PC-31.3: ECM Terminal Locations

Diagnostic Codes

Functional Test

Figure PC-31.4: Sensor Flange and Mounting Bracket

Figure PC-31.5: Engine Harness Connector P2

PC-32: Engine Speed/Timing Calibration

System Operation

Special Tools Required

Functional Test

PC-33: Injector Solenoids Circuit Test

System Operation

Figure PC-33.2: Injector Schematic

Figure PC-33.3: ECM Pin Locations

Diagnostic Codes

Functional Test

Figure PC-33.4: ET Automated Cylinder Cutout Test Screen

Figure PC-33.5: ET Injector Solenoids Test Screen

Figure PC-33.6: Engine Harness Injector Connector

Figure PC-33.7: Electronic Unit Injector Harness Terminals

PC-34: +5V Engine Pressure Sensor Voltage Supply Circuit Test

System Operation

Figure PC-34.2: +5V Engine Pressure Sensor Supply Schematic

Figure PC-34.3: ECM Terminal Locations

Diagnostic Codes

Functional Test

Figure PC-34.4: Engine Harness Connector P2

PC-35: Engine Pressure Sensor Open Or Short Circuit Test

System Operation

Figure PC-35.2: Engine Pressure Sensor Schematic

Figure PC-35.3: ECM Terminal Locations

Diagnostic Codes

Functional Test

Figure PC-35.4: Pressure Sensor Connector Terminals

Figure PC-35.5: Engine Harness Connector P2

PC-36: Engine Temperature Sensor Open Or Short Circuit Test

System Operation

Figure PC-36.2: Engine Temperature Sensor Schematic

Figure PC-36.3: ECM Terminal Locations

Diagnostic Codes

Functional Test

Figure PC-41.4: Engine and Vehicle Harness Connectors

PC-37: Event Codes Test

System Operation

Diagnostic Codes

Functional Test

PC-38: Multi-Torque Test

System Operation

Functional Test

A/C High Pressure Switch

Senses refrigerant pressure in the air conditioning system and (opens or closes) electrical contacts depending on this pressure to turn the cooling fan ON. This switch may or may not be connected to the ECM.

ATA (American Trucking Association) Data Link

A two-wire electrical connection for communication with other microprocessor based devices that are compatible with the American Trucking Association and SAE Standards (J1587 and J1708) such as trip recorders, electronic dashboards, powertrain controls, and maintenance systems. The Data Link is also the serial communication medium used for programming and troubleshooting with Caterpillar devices.

Accelerator Pedal Position

The ECM interpretation of the signal from the Accelerator Pedal Position Sensor.

Accelerator Pedal Position Sensor

An electronic sensor which is connected to the accelerator pedal and sends a Pulse Width Modulated Signal to the ECM.

Active Diagnostic Code

Describes a condition that is currently present to alert the driver or service technician of an abnormal engine operation parameter. Refer to Diagnostic Fault Code.

Aftermarket 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 in a circuit.

American Wire Gauge (AWG)

A measure of the diameter (and therefore the current carrying ability) of electrical wire. The smaller the AWG number, the larger the wire.

Anti-Lock Brake System (ABS)

Vehicle brake system that attempts to reduce wheel skid during brake operation. A power train electronic control can turn off the engine retarder if necessary, or signal the engine ECM to turn the engine retarder OFF.

Atmospheric Pressure Sensor

Analog sensor generates a signal proportional to atmospheric (barometric) air pressure in the crankcase and sends a signal to the ECM.

Auxiliary Retarder Relay

The brakes' solenoids are driven by an OEM installed relay, which is driven by the ECM.

Before Top Center (BTC)

The 180 degrees of crankshaft rotation before the piston reaches the very top of its travel (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 Driver Information Display (CAT ID)

A digital readout for operator viewing of vehicle and ECM monitored performance parameters.

Caterpillar Engine Monitoring

The part of the Caterpillar Electronic Engine Control that monitors Coolant Temperature, Oil Pressure, Intake Manifold Air Temperature and Coolant Level to alert the operator of detected problems. The Coolant Temperature, Intake Manifold Air 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. After market engine monitoring systems do not interface with the Caterpillar Electronic Engine Control.

Check Engine Lamp

Sometimes referred to as the "Diagnostic Lamp", it is used to alert the operator of the presence of an active event and is used to flash a diagnostic code.

Clutch Pedal Position Switch

This OEM supplied and installed switch is typically a limit switch mounted near the pedal and is usually adjustable. This switch is normally closed with the pedal released. Depressing the clutch will open the circuit.

Code

Refer to Diagnostic Fault Code and Diagnostic Event Code.

Cold Mode

A mode of engine operation where the timing is retarded and the low idle may be raised for engine protection, reduced smoke emissions and faster warm up time.

Coolant Level Sensor

This OEM installed sensor detects the absence/presence of coolant at the probe and sends a signal to the ECM.

Coolant Temperature Sensor

This sensor detects the engine coolant temperature for Cold Mode operation and Caterpillar Engine Monitoring (if Engine Monitoring is not programmed OFF).

Cooling Fan Cab Override Switch

This OEM supplied and installed switch overrides control of the cooling fan relay so the cooling fan operates continuously.

Cooling Fan Relay

This OEM supplied and installed relay is controlled by the ECM. The ECM controls the cooling fan relay based on coolant temperature, the engine retarder and OEM installed air conditioner high pressure switch (if installed).

Crankshaft Position Sensor

A sensor that measures crankshaft position, direction of rotation and engine rpm and sends signal to ECM.

Cruise Control Range

The range that the cruise control can operate within. Usually limited to the speed range anticipated on the open road. It is programmable using the Low Cruise and High Cruise Limits.

Custom Data

Part of the ECM stored fleet trip, it allows the vehicle owner to specify operating parameters for monitoring purposes while engine is in service.

Customer Specified Parameter

A parameter value that can be changed and whose value is set by the customer. Protected by Customer Passwords.

Data Link

Refer to ATA Data Link.

Desired RPM

An input to the electronic governor within the ECM. The electronic governor uses inputs from the Accelerator Pedal Position Sensor, Crankshaft Position Sensor and Customer Parameters to determine "Desired RPM".

Diagnostic Event Code

These codes indicate an event that describes an abnormal engine condition, such as an Idle Shutdown Occurrence. They are not necessarily (or usually) an indication of problems within the Electronic System.

Diagnostic Fault Code

Sometimes referred to as a "fault code". These codes indicate an electronic system malfunction or problem with the truck engine Electronic System.

Diagnostic Flash Code

These codes are flashed out using the Check Engine Lamp to indicate an electronic system malfunction or an event detected by the Electronic System ECM.

Diagnostic Lamp

Sometimes referred to as the "check engine lamp", it is used to alert the operator of the presence of an active diagnostic code.

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

Refer to 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.

Engine Control Module (ECM)

The engine control computer that provides power to the truck engine electronics. It accepts inputs that monitor and outputs that control or change to act as a governor to control engine rpm.

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.

Electronic Engine Control

The complete electronic system that monitors and controls engine operation under all conditions.

Electronic Technician (CAT ET)

A service tool software program to run on a personal computer (PC). This program replaced ECAP.

Engine Retarder Solenoids

This refers to the Engine Retarder installed by Caterpillar, with solenoids driven directly from the Caterpillar ECM, instead of driven through an OEM installed relay like the Auxiliary Brake.

Engine Speed/Timing Sensor

Provides a variable amplitude and 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).

Flash Code (FC)

The Caterpillar proprietary code numbers which are flashed out on the diagnostic lamp.

Flash Programming

A way of programming or updating an ECM with an Electronic Service Tool over the data link instead of replacing components.

Fleet Information Software (FIS)

A software program to run on a personal computer (PC). This program allows user to review and reset trip information including Maintenance Indicator information.

Fuel Position

An internal signal within the ECM, from the Electronic Governor to Fuel Injection Control. It is based on Desired RPM, FRC Fuel Limit, Rated Fuel Limit and engine rpm.

Fuel Ratio Control (FRC)

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 Limit (allows more fuel into cylinder).

Fuel Temperature Sensor

This sensor detects the fuel temperature. The ECM monitors the fuel temperature and adjusts calculated fuel rate accordingly.

Full Load Setting (FLS)

Number representing fuel system adjustment made at the factory to "fine tune" the fuel system maximum fuel delivery. Correct value for this parameter is stamped on the engine information ratings plate. This parameter must be programmed or a Diagnostic Code 253-02 Check Customer Or System Parameters (56) will be generated.

Full Torque Setting (FTS)

Similar to Full Load Setting. This parameter must be programmed or a Diagnostic Code 253-02 Check Customer Or-System Parameters (56) will be generated.

Gear Down Protection

Programmable High Gear Limits used to promote driving in higher gears for increased fuel economy.

Harness

The wiring bundle (loom) connecting all components of the Electronic System.

Hertz (Hz)

Measure of frequency in cycles per second.

Histogram

A bar graph indicating the relative frequency of vehicle operation in specific operating ranges.

Idle RPM Limit

Programmable parameter which indicates the maximum allowable engine rpm when an engine rpm is set using the Cruise/Idle On-Off switch and SET/RESUME switch.

Idle Shutdown Time

Programmable parameter which indicates time (in minutes) that the engine will idle before shutting down.

Idle/PTO Bump RPM

Programmable parameter indicating the amount which the engine RPM will be incremented/decremented when the Accel/Decel switches are briefly toggled.

Injector Codes

Four digit code etched on tappet or stamped on individual injectors of the electronic unit injectors.

Intake Manifold Air Temperature Sensor

This sensor detects the intake manifold air temperature. The ECM monitors the inlet air temperature and coolant temperature to adjust injection timing.

Integrated Electronic Controls

The engine is designed with the electronic controls as a necessary part of the system. The engine will not operate without the electronic controls.

J1922 Data Link

An SAE (Society of Automative Engineers) standard data link used to communicate between the electronic engine and power train components. Examples of power train components are ABS/Traction control or transmissions. This allows the powertrain component to control the engine during reduced traction or transmission shifts.

J1939 Data Link

An SAE (Society of Automotive Engineers) standard data link used to communicate between the electronic engine, the transmission, and/or powertrain controls.

Kickout Switch

Refers to the service brake and clutch switches used to "kickout" or exit cruise control, idle, or PTO set speeds.

Latch Mode

Programmable parameter option for control of the exhaust brake. The exhaust brake engages when the service brake pedal is depressed and remains engaged until the control detects a change in a control input.

Logged Diagnostic Codes

Describes codes which are stored in memory. They are meant to be an indicator of possible causes for intermittent problems. Refer to Diagnostic Fault Code.

Oil Pressure Sensor

This sensor measures engine oil pressure and sends a signal to the ECM as part of Caterpillar Engine Monitoring.

Open Circuit

Condition where an electrical wire or connection is broken or a switch is open, 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 or limit which determines the characteristics or behavior of the engine and/or vehicle.

Parameter Identifier (PID)

Two or three digit code which is assigned to each component to identify data via data link to ECM.

Passive Magnetic Vehicle Speed Sensor

A vehicle speed sensor not requiring a power and ground connection. It produces a signal based on the change in magnetic flux of a ferrous metal gear near the sensing tip.

Password

A group of numeric or alpha-numeric characters, designed to restrict access to parameters. The electronic 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 Accelerator Pedal Position Sensor

This sensor measures pedal position and sends a signal to the ECM. The sensor is mounted on an accelerator pedal assembly.

Personality Module or Ratings Personality Module

The module attached inside of the ECM which contains all the instructions (software) for the ECM and performance maps for a specific power family.

Power Take Off (PTO)

Operates with the cruise control switches and Dedicated PTO On/Off switch. This mode permits setting constant engine speeds, or varying speed with either the cab accelerator pedal or a remote accelerator.

Powertrain Data Link

Refer to J1922 Data Link.

Pro-Link

A hand-held electronic service tool manufactured by Micro Processor Systems, Inc. (MPSI). Available with a Caterpillar cartridge to service Caterpillar electronic engines.

Progressive Shifting

Shifting up through the lower gears quickly by not using excessive engine rpm in each gear. Shifts are made above peak torque but below rated rpm. Using excessive engine (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.

POT Configuration

Programmable parameter which determines the use of the ECM several inputs and outputs for PTO applications.

Pulse Width Modulation (PWM)

A signal consisting of variable width pulses at fixed intervals, whose ratio of "TIME ON" versus total "TIME OFF" can be varied (also referred to as "duty cycle")

Rated Fuel Limit

Indicates the maximum allowable fuel position (longest injection pulse). It will produce rated power for this engine configuration.

Reference Voltage

A regulated, unchanging voltage supplied by the ECM to a sensor. The reference voltage is used by the sensor to generate a signal voltage.

Remote Station Operation

Engine speed control from a location outside of the vehicle cab, typically for some type of PTO operation for pumping or other application using engine power.

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).

Retarder Solenoids

This refers to the Engine Retarder, installed by Caterpillar, with solenoids driven directly from the Caterpillar ECM, instead of driven through an OEM installed relay like the Auxiliary Retarder.

Sensor

A device used to detect and convert a change in pressure, temperature, or mechanical movement into an electrical signal.

Service Brake Pedal Position Brake Switch

This OEM supplied and installed switch is typically a pressure switch. This switch is normally closed with the pedal released. Depressing the brake will open the circuit.

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, unwanted change in engine rpm.

Standard SAE Diagnostic Communications Data Link

Refer to ATA Data Link.

Subsystem

As used here, it is a part of the Electronic 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.

System Configuration Parameters

Parameters which affect power rating family or emissions.

"T" Harness

A test harness designed to connect into vehicle or engine harness which allows normal circuit operation while providing a breakout or "T" to measure signals.

Theft Deterrent

A feature which uses a four digit code to prevent the engine from starting. Requires a password to be entered via CAT ID display.

Timing Calibration

The adjustment of an electrical signal as a means of correcting timing error between the crankshaft and the Crankshaft Position Sensor.

Torque Limit

Programmable parameter which limits the maximum torque based on parameter programming. An OEM installed Torque Limit Switch is required.

Total Tattletale

Total number of changes to all Customer Specified Parameters stored in the ECM.

Transmission Style

Programmable parameter that designates the type of transmission in the vehicle and the circuits connected to the ECM. The transmission relay, cruise control, idle/PTO, and exhaust brake operation are affected by this parameter setting.

Trip Recorder

An after market device dedicated to recording vehicle and engine operating parameters during vehicle service. Used to analyze driving habits and produce driver logs.

Vehicle Speed Calibration

Programmable parameter used by the ECM to scale the vehicle speed signal into miles per hour (or kilometers per hour).

Vehicle Speed Sensor

An electromagnetic pickup that measures vehicle speed from the rotation of gear teeth in the drive train of the vehicle.