Automotive Emission Control Systems – Must Perform One Important Job

Automotive Emission Control Systems - Must Perform One Important Job
Automotive Emission Control Systems - Must Perform One Important Job

Automotive emission control systems help control fuel fumes; while cleaning engine producing exhaust gases.

Consequently, these systems have been efficient in reducing air pollution caused by automotive engines.

Also, increased engine efficiency and lighter vehicle construction; has also contributed to help reduce emissions.

So, automotive emission control systems depends on a series of chemical reactions; sensors and vacuum control solenoids to operate correctly.

In time, chemical reactions fade as the devices lose their effectiveness. Consequently, either of these failures will cause a check engine light to come on.

Emission Control Systems
Excessive Idling Wastes Money And Fuel

In addition, excessive idling wastes money and fuel; while producing greenhouse gases that contribute to climate change.

Finally, your emission system controls the emissions, exhaust and pollutants; using an array of sensors, computerized engine controls and exhaust components.

Engine Generated Pollutants Come From Three Sources;

  • Tailpipe exhaust
  • Crankcase blow by vapours
  • Fuel vapours that evaporate from the fuel tank

Air Pollution Gases Produced By Engines Consist Of;

  • Carbon monoxide
  • Hydrocarbons
  • Carbon dioxide
  • Nitrogen oxide

Most Emission Control Systems Consist Of;

  • Air Pump
  • Catalytic Converter
  • Check Engine Light (CIL)
  • Exhaust Gas Recirculation (EGR)
  • Automotive Filters
  • Gas Cap
  • Evaporative System
  • Mass Air Flow Sensor (MAF)
  • OBD II System
  • Oxygen Sensor (O2)

Air Pump

Air injection systems have become more diverse in nature; sometimes using the on board computer to control system operations. Similarly, some engines use pulse air systems; that do not use a pump.

Air Injection Smog Pump
Air Injection Smog Pump

As obsolete as this technology seems, some late model vehicles use a high tech air injection system. Also, using an electric air pump; controlled by the vehicles Powertrain Control Module (PCM).

Catalytic Converter

The catalytic converter looks like a muffler. It is located in the exhaust system ahead of the muffler. Inside the converter are pellets or a honeycomb made of platinum or palladium. The platinum or palladium is used as a catalyst.

Catalytic Converter
Catalytic Converter

Consequently, as exhaust gases are passed over the catalyst they are chemically oxidized or converted to carbon dioxide and water. So, as the converter works to clean the exhaust, it develops heat. The dirtier the exhaust, the harder the converter works; and the more heat that is developed. Finally, if the converter works too hard to clean a dirty exhaust it will destroy itself.

(EGR) Valve

So, the (EGR) valve has no recommended replacement or inspection interval, but that doesn’t mean it won’t cause trouble.

(EGR) Valve
(EGR) Valve

As a result, (EGR) reduces the formation of oxides of nitrogen, by diluting the air/fuel mixture with exhaust. As an added benefit, (EGR) also helps prevent detonation.

Filter Systems

So, the oil filter traps harmful debris from being recirculated back through the engines lubrication system. Also, the air filter stops harmful dirt particles from entering the engines air intake system; where they may cause engine damage.

Paper Air Filter Close Up
Paper Air Filter Close Up

The crankcase breather filter cleans the air pulled into the engine crankcase; by using the positive crankcase ventilation (PCV) system. The fuel filter cleans the fuel before it reaches the fuel delivery system; namely the fuel injectors. Furthermore, the canister filter cleans the air entering the carbon canister, that is part of the emission control system.

Gas Cap

Above all, a gas cap seals liquid fuel and fumes; from escaping from the fuel tank.

Gas Cap
Gas Cap

The gas cap is also an integral part of the onboard diagnostics system (OBD-II) and emission control systems.

Evaporative System

The evaporative system, sometimes abbreviated as (EVAP), consists of the;

  • Fuel cap
  • Fuel tank
  • Carbon canister
  • Canister purge valve
  • Interconnecting lines and hoses

So, sealing the fuel tank is not as simple as it sounds. A fuel tank must have some type of venting so air can enter to replace the fuel leaving the tank.

Emission Control Systems
Automotive Emission Control Systems

If the fuel tank were sealed tight, the fuel pump could create enough negative pressure to collapse it. This system contains fuel vapours (hydrocarbons) but; instead of releasing them into the atmosphere; it stores them in a carbon canister. The collected vapours are then routed to the engine; where they can be burned.

Mass Air Flow Sensor (MAF)

Finally, a mass air flow sensor monitors airflow that enters the engine.

Mass Air Flow (MAF) Sensor Location
Mass Air Flow (MAF) Sensor Location


The SERVICE ENGINE SOON or CHECK ENGINE LIGHT has several modes. On Board Diagnostics (OBD)

P0400-P0499 – Auxiliary Emissions Controls. OBD-II

Automotive Emission Control Systems
Check Engine Light

Consequently, It can indicate a:

  • Normally functioning system
  • A system that requires prompt attention
  • A system that needs immediate attention

Oxygen Sensor (O2)

An oxygen sensor is designed to monitor engine exhaust gases.

Automotive Emission Control Systems
Oxygen Sensor (O2)


Finally, computerized control ensures the most efficient operation of the system. In addition, computer controlled fuel injection systems ensure a more precise air fuel mixture. As a result, creating greater efficiency in combustion while lowering pollutants.

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