Actron CP9035 Insrucciones página 15

The PCM is programmed with a complex list of lookup tables and instructions
telling the computer how to control the various engine systems based on
information received. To do its job, the computer uses many different sensors to
know what is happening and then controls the various systems through a
network of actuators throughout the vehicle.
Sensors and switches give the computer information
Sensors and Switches are devices that measure operating conditions and
operator demands. These conditions and demands are translated into signals
the computer can understand. Some examples of sensors are: thermistors (for
temperature readings), potentiometers (like a throttle position sensor), and
signal generators (such as an 02 sensor). A network of sensors delivers informa-
tion to the computer. The PCM converts these electrical signals into data that the
computer can understand. Sensors are referred to as input devices because
they send information to the PCM.
Sensors monitor key things such as:
Engine Temperature
Throttle position (driver demand)
Incoming Air Temperature
Rich or Lean Exhaust gas condition
Actuators are devices controlled by the computer to perform a specific func-
tions. The PCM sends signals known as output to the actuators to control them.
Relays are used to control electrical circuits such as the electric coolant fans, air
conditioning clutch, and fuel pumps. Actuators also include solenoid types (such
as fuel injector valves) and small motors (such as the Idle Speed Control). Not
all of the computer's outgoing signals are routed to actuators. Sometimes
information is sent to other system computers like transmission, brakes, ignition
modules, and trip computers. Signals running from the PCM to other compo-
nents are also called "outputs."
How the computer controls fuel delivery
Engine operation and emissions performance depends upon precise fuel
delivery and ignition control. Early computer systems controlled fuel by electroni-
cally adjusting the carburetor metering and jet systems. However, this was
replaced by the more precise solenoid type actuator known as fuel injectors.
In an electronically carbureted system, the computer simply controls fuel flow
COMPUTER BASICS
Intake Manifold Vacuum (engine load)
RPM
Volume of Incoming air
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