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ISC
Idle Speed Control. This
refers to a small electric
stepper motor mounted on
the throttle body and
controlled by the ECA. (See
Stepper Motor definition.)
The ISC motor moves a
spindle back and forth.
When the throttle is
released during idle, it rests
on this spindle. The ECA
can control idle speed by
adjusting this spindle
position. The ECA
determines the desired idle
speed by looking at coolant
temperature, engine load
and RPM. The Idle
Tracking Switch (see ITS
definition) is built-into the
tip of the spindle. The ISC
motor also performs
dashpot and anti-dieseling
functions.
ISC-BPA
Idle Speed Control By-Pass
Air valve. This is a solenoid
type actuator mounted on
the throttle body and
controlled by the ECA with
a duty cycle type signal.
(See Duty Cycle definition.)
It is used for idle speed
control. The valve operates
by regulating the amount of
incoming air bypassing the
closed throttle plate. When
the ECA increases control
signal duty cycle, more air
is bypassed through the
valve for faster idle speed.
The ECA determines the
desired idle speed by
looking at coolant
temperature, engine load
and RPM. The ISC-BPA
also performs dashpot and
anti-dieseling functions.
ITS
Idle Tracking Switch. This
is a mechanical switch
built-into the tip of the Idle
Speed Control motor
spindle. (See ISC
definition.) The ECA uses
this switch to identify
closed throttle condition.
The switch is open when
the throttle rests on it
(closed throttle position).
The MCU systems use a
similar acting ITS which is
mounted on the carburetor
near the throttle linkage.
IVSC
Integrated Vehicle Speed
Control. The name given to
the speed control function
when it is built-into the ECA
and not controlled by an
outside module.
KAPWR
Keep Alive Power. A power
connection running from
the ECA directly to the
vehicle battery. This power
is used energize the
“learning memory” circuits
inside the ECA – even
when the ignition key is off.
The memory stores
adjustment information the
ECA uses to compensate
for aging sensors, and the
like. The information is lost
when power is
disconnected, such as
when the vehicle battery is
removed for service, but
can be “relearned” by the
ECA during normal engine
operation.
Keypower
The circuit which provides
power to the engine control
system. Includes the
ignition key switch.
KS
Knock Sensor. The ECA
uses this device to detect
engine detonation
(knocking). When spark
knock occurs, the sensor
sends a pulsing signal. The
ECA than retards spark
advance until no detonation
is sensed. The sensor
contains a piezoelectric
element and is threaded
into the engine block.
Vibrating the element
generates the signal.
Special construction makes
the element only sensitive
to the engine vibrations
associated with knocking.
LED
Light Emitting Diode. A
semiconductor device
which acts like a miniature
light bulb. When a small
voltage is applied, the LED
glows. LED’s may be red,
orange or yellow or green.
They are often used as
indicators or in numeric
displays.
LUS
Lock-Up solenoid. Located
in automatic transaxle. The
ECA uses this solenoid to
control the lock-up clutch in
the torque converter. The
ECA
will engage or release lock-
up depending upon engine
operation.
MAF
Mass Air Flow sensor. This
sensor measures the
amount of air entering the
engine and sends a voltage
signal to the ECA. The
signal voltage increases
when the amount of
incoming air goes up. This
gives the ECA information
required for control of fuel
delivery, spark advance
and EGR flow.
MAP
Manifold Absolute Pressure
sensor. This sensor
measures manifold vacuum
and sends a frequency
signal to the ECA. This
gives the ECA information
on engine load for control
of fuel delivery, spark
advance and EGR flow.
MCCA
Message Center Control
Assembly. A dashboard
mounted electronic display
giving the driver trip
computer and vehicle
status information.
Exchanges information with
the ECA by using the Data
Communications Link
(DCL).
MCU
Microprocessor Control
Unit. A computerized
engine control module used
on many Ford vehicles
between 1980 and 1984.
The MCU system consists
of a computerized control
module (MCU), sensors
and actuators. The system
controls fuel delivery and
thermactor air flow. Later
versions of MCU also
controlled canister purge
(see CANP definition),
spark retard and idle
speed. The MCU system
was eventually replaced by
EEC-IV.
MLP
Manual Lever Position
sensor. Connected to gear
shift lever. Sends a voltage
signal to the ECA indicating
lever position (P, R, N, D, 2
or 1).
Mode
A type of operating
condition, such as “idle
mode” or “cruise mode.”
