Instructions Manual

Glossary
A-3
throttle position, coolant temperature,
engine load, vehicle speed, Park/Neutral
switch position, and knock
sensorcondition
.
EVAP:
Evaporative
Emissions System.
Hall
Effect Sensor:
Any
of a type of sensor utilizing a
permanent magnet and a transistorized
Hall Effect switch. Hall Effect type
sensors may be used to measure
speed and position of the crankshaft or
camshaft — for spark timing and fuel
injector control.
HO2S:
Heated
Oxygen Sensor. See O2S.
IAC:
Idle
Air Control. A device mounted on
the throttle body which adjusts the
amount of air bypassing a closed
throttle so that the PCM can control idle
speed.
ICM:
Ignition
Control Module.
I/M:
Inspection
and Maintenance.
ISC:
Idle
Speed Control. A small electric
motor mounted on the throttle body and
controlled by the PCM. The PCM can
control idle speed by commanding the
ISC to adjust its position.
Knock:
Uncontrolled
ignition of the air/fuel
mixture in the cylinder. Also referred to
as detonation or ping. Knock indicates
extreme cylinder pressures or
“hotspots” which are causing the
air/fuel mixture to detonate prematurely.
Knock Sensor (KS):
Used
to detect engine detonation or
“knock.” The sensor contains a
piezoelectric element and is threaded
into the engine block. Special
construction makes the element
sensitive only to engine vibrations
associated with detonation.
KOEO:
Key
On, Engine Off.
KOER:
Key
On, Engine Running.
LCD:
Liquid
Crystal Display.
LT:
Long
Term fuel trim.
M/T:
Manual
transmission or manual
transaxle.
MAF:
Mass
Air Flow Sensor. Measures the
amount and density of air entering the
engine and sends a frequency or
voltage signal to the PCM. The PCM
uses this signal in its fuel delivery
calculations.
MAP:
Manifold
Absolute Pressure Sensor.
Measures intake manifold vacuum or
pressure and sends a frequency or
voltage signal (depending on sensor
type)
to the PCM. This gives the PCM
information on engine load for control
of fuel delivery, spark advance, and
EGR flow.
MAT:
Manifold
Air Temperature sensor . A
resistance sensor in the intake
manifold that sends a voltage signal to
the PCM indicating the temperature of
the incoming air. The PCM uses this
signal for fuel delivery calculations.
MIL:
Malfunction
Indicator Lamp. The MIL is
most commonly known as the Check
Engine Light. Also labeled Service
Engine Soon, Power Loss or Power
Limited.
Monitor:
A
test performed by the on-board
computer to verify proper operation of
emission related systems or
components.
MPFI
or MFI:
Multi-Port
Fuel Injection. MPFI is a fuel
injection system using one (or more)
injector(s) for each cylinder. The
injectors are mounted in the intake
manifold, and fired in groups rather
than individually.