Engines Mechanical and Electrical Systems
Power steering relies on a simple principle- a hydraulic pump
running off a belt driven by the engine places a small amount of fluid
under pressure, which in turn assists the steering mechanism in
directing the tires as you turn the steering wheel. The system
typically includes a pump, a pressure hose assembly, a control
valve, and a return line.
Powertrain Control Module
The PCM is designed to maintain exhaust emission levels to
Federal/California/other standards while providing excellent
driveability and fuel efficiency. The PCM monitors numerous
engine and vehicle functions.
Secondary Air Injection System (A.I.R.)
The Secondary Air Injection (AIR) System reduces exhaust
emissions following initial engine start up. The powertrain
control module (PCM) activates the AIR system by suppling
a ground to the AIR pump relay and AIR solenoid relay
simultaneously. This action closes the internal contacts of
the AIR pump relay.
PCV Valve (Positive Crankcase Ventilation)
A crankcase ventilation system is used to consume
crankcase vapors in the combustion process instead of
venting them to atmosphere. Fresh air from the throttle
body is supplied to the crankcase.
ABS - Stands for Anti-lock Brakes. If wheel slip is
detected by the computer, the ABS system pulses the
brake pressure to the wheels. Many parts make up this
system. A computer, sensors, motors, wiring, valves.
Airbags - Supplemental Inflatable Restraint -
Also know as SIR. Very important safety item used in
conjunction with the seat belts system. Air bags are in
more and more places in todays cars and trucks. Not
only in the steering wheel and passenger front dash,
but also in the side pillars next to the front seats, in the
side of the seats, above your head- called curtain air
bags, rear occupant side air bags.
Diagnostic computer scan tools - There are
many types of scan tools. From the most basic models
you can purchase at most auto parts stores, to the most
high-end, cutting edge tools we use at the shop. These
are invaluable tools to diagnose almost any system in
todays vehicles. Depending on the capability of the
scanner, you can read trouble computer trouble codes
when the check engine light has come on with
the most basic scanner, and manipulating and
controlling most vehicle system for testing operation
and diagnostic purposes on the most advanced and
Basic electrical theory - Most conventional
vehicles use a 12 volt negative ground electrical
system. The battery is the main component that is used
to start the vehicle. The alternator is used to supply
power to the cars electrical systems and to keep the
battery charged. Testing electrical circuits is done with
a Digital volt Ohm Meter (DVOM).
Engine Data Sensors - There are many sensors on todays vehicles
to monitor all aspects of engine operations. From the fuel system, spark
control, electronic throttle, engine timing, to emissions controls.
Exhaust Gas recirculation - Known as EGR. This is a very
important component in the vehicle emissions system that has been
around for decades in various forms.
Fuel Injection - High pressure fuel is supplied by an electric pump in the
fuel tank. Pressure is regulated by the fuel pressure regulator. The fuel
injector is a solenoid operated device, controlled by the Powertrain Control
Module (PCM), that meters pressurized fuel to a single engine cylinder.
Front and Rear Brake Operation
The hydraulic brake system consists of the following:
Hydraulic Brake Master Cylinder Fluid Reservoir: Contains supply
of brake fluid for the hydraulic brake system.
The electronic ignition system produces a high energy spark.
This spark is used to ignite the compressed air/fuel mixture at
the correct time. This provides optimal performance, fuel
economy, and control of exhaust emissions. The cylinder that is
at TDC of the compression stroke is called the event cylinder.
The cylinder that is at TDC of the exhaust stroke is called the
Stability or Stabililtrak System
The vehicle stability enhancement system (VSES) provides
added stability during aggressive maneuvers. Yaw rate is the
rate of rotation about the vehicle's vertical axis. The system is
activated when the electronic brake control module (EBCM)
determines that the desired yaw rate does not match the
actual yaw rate as measured by the yaw rate sensor.
The evaporative emission System (EVAP)
This control system limits the fuel vapors from escaping into the
atmosphere. The EVAP transfers the fuel vapors from the sealed
fuel tank to an activated carbon storage device, the EVAP
canister. The EVAP canister stores the vapors until the engine is
able to use the extra fuel vapor. When the engine is able to use
the extra fuel vapor, the intake air flow purges the fuel vapor from
the carbon element and then the normal combustion process
consumes the fuel vapor.
Automotive Systems Description And Operation Index
Radio Shows LOC or INOP
Learn how the radio theft system works on your car or
truck. Get the code to unlock your radio.
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