Actron CP9035 Insrucciones página 46

REFERENCE GLOSSARY
Fuel Pump Signal:
This is a wire between the PCM and
the fuel pump motor power terminal.
The PCM uses this signal to verify
when voltage is at the fuel pump (for
diagnosing fuel pump problems).
Gear Switches:
These are switches (usually two)
located inside certain automatic
transmissions. The PCM monitors the
switches to determine what transmis-
sion gear is engaged. The switches are
activated by hydraulic pressure and
may be normally open or closed,
depending on the vehicle. The PCM
uses gear information for control of the
torque converter clutch, some emis-
sion systems, and for transmission
diagnostic purposes.
Ground:
Ground is the return path for current to
flow back to its source (Usually the
negative battery terminal). It is also the
reference point from which voltage
measurements are made (the connec-
tion place for the negative (-) test lead
from a voltmeter).
Hall Effect Sensor:
This sensor is a three wire-type of
sensor containing electronic circuitry.
Two wires supply power and ground,
while a third wire carries the sensor
signal back to the PCM. The sensor
consists of a permanent magnet and a
small module containing a transistor-
ized Hall Effect switch. A small air gap
separates the sensor and the magnet.
The magnetic field causes the Hall
switch to turn on and send out a low
voltage signal. If a metal strip (iron or
steel) is placed in the gap, it will block
the magnetic field from reaching the
Hall device. This causes the Hall
switch to turn off and send a high
voltage signal out on the signal wire.
The metal strips (blades) are part of a
cup or disk attached to a rotating
8-5
component such as the crankshaft or
camshaft. As the blades pass through
the sensor gap, the signal voltage will
switch high and low, creating a series
of pulses. The PCM determines the
speed of rotation by measuring how
fast pulses appear. 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.
IAC:
Idle Air Control. This is 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. The IAC is a stepper
motor that moves a pintle within the air
bypass passage. When the PCM
wants to change idle speed, it will
move the pintle backwards for more air
and a fast idle, or forward for less air
and a slower idle. See also "Stepper
Motor" definition.
ICM:
Ignition Control Module.
Inputs:
Electrical signals running into the PCM.
These signals come from sensors,
switches or other electronic modules.
They give the PCM information about
vehicle operation.
ISC:
Idle Speed Control. This refers to a
small electric motor mounted on the
throttle body and controlled by the
PCM. The ISC motor moves a spindle
back and forth. When the throttle is
released during idle, it rests on this
spindle. The PCM can control idle
speed by adjusting this spindle
position. The PCM determines the
desired idle speed by looking at battery
voltage, coolant temperature, engine