10 TERMINOLOGY 589
diagnostics software for chassis related components
and systems.
Low speed digital inputs – Switched sensor inputs
that generate an on/off (high/low) signal to the ECM.
The input to the ECM from the sensor could be from
a high input source switch (usually 5 or 12 volts) or
from a grounding switch that grounds the signal from
a current limiting resistor in the ECM that creates a low
signal (0 volts).
Lubricity – Lubricity is the ability of a substance
to reduce friction between solid surfaces in relative
motion under loaded conditions.
Lug (engine) – A condition when the engine is
operating at or below maximum torque speed.
Manifold Absolute Pressure (MAP) – Intake
manifold pressure (boost pres su re).
Manifold Absolute Pressure (MAP) sensor –
A variable capacitance sensor that senses intake
manifold pressure.
Manometer – A double-leg liquid-column gauge, or a
single inclined gauge, used to measure the difference
between two fluid pressures. Typically, a manometer
records in inches of water.
Master Diagnostics (MD) – The diagnostics software
for engine related components and systems to use on
the electronic service tool or personal computer.
Manifold Ai r Temperature (MAT) – Intake manifold
air temperature
Manifold Air Temperature (MAT) sensor – A
thermistor style sensor housed in the intake manifold
used to indicate air temperature after passing through
the charge air cooler.
Microprocessor – An integrated circuit in a
microcomputer that controls information flow.
Nitrogen Oxides (NO
x
)–Nitrogen oxides form by
a reaction between nitrogen and oxygen at high
temperatures and pressures in the combustion
chamber.
Normally closed – Refers to a switch that remains
closed when no control force is acting on it.
Normally open – Refers to a switch that remains open
when no control force is acting on it.
Ohm (Ω)–The unit of resistance. One ohm is the
value o f resistance through which a potential of one
volt will maintain a curren t of one ampere. (SAE J 12 13
NOV82)
On demand test – A self test that the technician
initiates using the EST. It is run from a pro gram in the
processor.
Output Circuit Check (OCC) – An On demand test
done during an E ngine O FF self test to check the
continuity of selected actuators.
Output State Check (OSC) – An On demand te st
that forces the processor to activate actuators (High
or Low) for additional diagnostics.
pH – A measure o f the acidity or alkalinity of a solution.
Particulate matter – Particula te matte r includes
mostly burned particles of fuel and engine oil.
Piezometer – An instrument for measuring fluid
pressure.
Positive On Shaft Excluder (POSE) – It is a separate
piece from t he rest of the front or rear seal used to
keep out dust / debris.
Potentiometer – A potentiometer is a variable voltage
divider that senses the position of a mechanical
component. A reference voltage is applied to one
end of the potentiome ter. M echanical rotary or linear
motion moves the wiper along the resistance material,
changing voltag e at each point along the resistive
material. Voltage is proportional to the amount of
mechanical movement.
Power – Power is a measure of the rate at which work
is done. Compare with Torque.
Power Take Off (PTO) – Accessory output, usually
from the transmission, used to power a hydraulic
pump for a s pe cial auxilia ry feature (garbage packing,
lift equipment, etc.).
Pulse Width Modulation (PWM) – Thetimethatan
actuator, such as an injector, rem ains energized .
Random Access Memory (RAM) – Computer
memory that stores information. Information can
be written to and re ad from RAM. Input informa tio n
(current engine speed or temperature) can be stored
in RAM to be compared to values stored in Read Only
Memory (ROM). All memory in RAM is lost when the
ignition switch is turned off.
Rated gross horsepower – Engine gross
horsepower at rated speed as declared by the
manufacturer. (SAE J1995 JUN90)
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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