General Information - On-Board Computer and Emission Control System

Emission control systems and components are integral parts of the engine management system under the hood of most cars, trucks, vans and SUVs produced today. Emission control systems are Federally-mandated to help reduce emissions, improve fuel economy and protect the environment.

At the heart of your vehicle's engine management system is the on-board computer, known as the Powertrain Control Module (PCM). The PCM's job is to respond to and alter various engine parameters as needed to maintain optimal efficiency, performance and help reduce emissions. These parameters include speed, temperature, load, etc.

A number of sensors provide information to the PCM, enabling it to monitor the above operating parameters. The PCM is also connected to a variety of "output actuators," or mechanical devices, that respond to these conditions. These include the fuel injectors, ignition coils, and various relays and solenoids. Relays regulate the flow of electricity to various components; solenoids regulate air, coolant, or vacuum flow. The main conditions and systems that the PCM monitors include air injection, the catalytic converter, exhaust gas recirculation, intake manifold, and positive crankcase ventilation.

In order to monitor and analyze engine management systems, most home technicians use hand-held scanners. A scanner can tell you nearly anything you need to know about your engine management system. Although scanners are powerful and versatile tools, you must be certain that the brand of scanning device you plan to use matches the year, make and model of the vehicle you are working on.

As previously stated, the on-board computer system (or PCM) together with various sensors gather information about your engine. While your engine is running, it sends a constant stream of information via the sensors to the PCM. But modern PCM's not only monitor information and act on it to insure top engine performance; they can actually predict component or system failure.

A Vehicle Emissions Control Information label is located in the engine compartment that specifies essential tune-up and adjustment procedures. It also has a vacuum hose diagram that shows how vacuum-controlled emissions components are connected. If your car, truck, van or SUV is still under warranty, an even longer warranty covers almost all of the components of your emissions system. It is not a good idea to fix emissions-control problems yourself, simply because your vehicle, unless it is very old, is probably still covered by the emissions warranty. Damaging emissions components will void this warranty, so beware. As long as the system is still under warranty, have a dealer service department make any repairs or replace any parts.

Remember: the emissions control system and engine diagnostic system on your truck, van, car or SUV will help you get better mileage, better performance and better efficiency from your engine. But this system also helps all of us by allowing fewer pollutants into the air. So be sure to take advantage of this special emissions warranty which is often up to 70,000 or seven years.