Desired RPM

TM 9-2320-312-24-2

Systems Operation Section

Fuel Ratio Control (FRC) The FRC is a limit that

Desired RPM The desired rpm is input to the

is based on the control of the fuel to air ratio. The

electronic governor within the ECM. The electronic

FRC is used for emission control. When the ECM

governor uses the signal from the Accelerator Pedal

senses a higher turbocharger outlet pressure, the

Position Sensor, the Engine Speed Sensor, the

ECM increases the limit for the FRC in order to allow

Cruise Control, and the Customer Parameters in

more fuel into the cylinders.

order to determine desired rpm.

Fuel Position The fuel position is a signal within

Diagnostic Code A diagnostic code is sometimes

the ECM. The signal is from the electronic governor.

called a fault code. A diagnostic code is an

The signal goes to the fuel injection control. The

indication of a problem or event in the electrical

signal is based on the desired engine speed, the

engine systems.

FRC, the rated position, and the actual engine

speed.

Diagnostic Lamp A diagnostic lamp is sometimes

called the check engine light. The diagnostic lamp

Harness The harness is the bundle of wiring

is used to warn the operator of the presence of an

that connects all the components of the electrical

active diagnostic code.

engine system.

Direct Current (DC) Direct current is the type of

Hertz (Hz) Hz is the measure of frequency in

current that flows consistently in only one direction.

cycles per second.

Duty Cycle See Pulse Width Modulation.

High Pressure Oil Manifold The high pressure

oil manifold is an oil gallery that is added to the

Engine Control Module (ECM) The ECM is the

cylinder head in order to supply the unit injectors

engine's control computer. The ECM provides power

with high pressure oil.

to the electronics. The ECM monitors data that is

input from the engine's sensors. The ECM acts as a

High Pressure Oil Pump The high pressure oil

governor in order to control engine rpm.

pump is an axial piston pump that is driven by

gears. The high pressure oil pump is used to raise

Electronic Engine Control The electronic engine

the engine oil pressure in order to activate the unit

control is a complete electronic system. The

injectors. The amount of oil pressure that is required

electronic engine control monitors the engine

to activate the unit injectors is called the actuation

operation under all conditions. The electronic

pressure.

engine control also controls the engine operation

under all conditions.

Hydraulic Electronic Unit Injector System (HEUI)

The HEUI is a fuel system that uses a hydraulically

Electronic Technician (ET) The electronic service

actuated, electronically controlled unit injector. The

tool of choice for Caterpillar engines is ET. ET is

system combines the pumping, electronic fuel

used for diagnosing a variety of electronic controls.

metering and injecting elements in a single unit.

ET is also used for programming a variety of

electronic controls.

Injection Actuation Pressure Control Valve (IAP

Control Valve) The injection actuation pressure

Estimated Dynamic Timing Estimated dynamic

control valve is a variable valve. The valve is used

timing is the estimate of actual injection timing by

to maintain the proper oil pressure in the engine

the ECM.

high pressure oil gallery. The valve is controlled by

the ECM.

Enable Signal for the Exhaust Brake The enable

signal for the exhaust brake interfaces with the ECM

Injection Actuation Pressure Sensor (IAP) The

to the engine retarder. This prevents the operation

injection actuation pressure sensor is a sensor that

of the exhaust brake under unsafe engine operating

measures hydraulic oil pressure. The sensor also

conditions.

sends a signal to the ECM.

Failure Mode Identifier (FMI) The FMI describes

Inlet Air Temperature Sensor The inlet air

the type of failure that was experienced by the

temperature sensor is a sensor that measures the

component. The codes for the FMI were adopted

inlet air temperature. The sensor also sends a signal

from the standard practices of SAE (J1587

to the electronic control module (ECM).

diagnostics).

Open Circuit An open circuit is a broken electrical

Flash Memory See the Personality Module.

wire connection. The signal or the supply voltage

cannot reach the intended destination.