GM Vehicle systems operations and descriptions.
Engines Mechanical and
Electrical Systems
Other Automotive systems
Power Steering
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...
Chevy, Pontiac, Buick, Cadillac, GMC, Oldsmobile
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...
Tire Pressure Monitor System
The tire pressure monitor system in todays cars use a radio frequency (RF)
transmitter ( Tire Pressure Sensor ) in each wheel valve stem to relay pressure
information to the module...
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...
Click on the links above for information on some of the different GM vehicle systems.
From engine mechanical, to electrical, to body control systems.
WARNING LIGHTS
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,  
to manipulating and controlling most vehicle system for testing operation and diagnostic  
purposes on the most advanced and expensive types...
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)...
Displacement on Demand - Provides maximum fuel economy under light load driving  
conditions. The engine will operate on 8 cylinders, or V8 mode, during engine starting, engine  
idling, and medium to heavy throttle applications...
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....  
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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.
Electronic Ignition
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 waste cylinder.The
EI system consists of the following components:
Stability or Stabliltrak 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.
Belts  |  Brakes  |  Tires  |  Maintenance  |  Electrical  |  ABS  |  Airbags  |  Ignition  |  Fuel Injection  |  Power Steering  |  Transmission
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