What does it mean exactly when the "Check Engine" warning light comes on?
When the "Check Engine" indicator comes on and stays on it means that the vehicle's on-board computer (commonly called Electronic Control Module, or ECM) has detected a problem with one of the emission control systems it monitors. This could be a minor problem but it could also be serious. Let's take a look first at how this warning light came about.
Development of emission control devices
All over the media there's talk of pollution and smog problems in major cities. California is one of the places hardest hit with this problem and is a leader in the fight against pollution caused by automobiles. Since 1988 the California Air Resources Board (CARB) requires that all vehicles sold in California be equipped with an emission control monitoring system known as "On-Board Diagnostics" – first generation is called OBD I. Regulations say that if a malfunction is detected, the system must illuminate a warning lamp on the vehicle instrument panel to alert the driver. On top of the warning light, malfunction codes are kept in the on-board computer to help repair technicians locate and fix the problem.
OBD I controls and checks the proper gas-air mixture ratio, the exhaust gas recycling (EGR valve), the oxygen sensor, and other electrical components of the emission control system. That's when the notorious "Check Engine" indicator light makes its debut on the instrument panel, but it doesn't come on as often as the second generation diagnostics system does, that is OBD II.
In 1996 CARB put new regulations into effect, and the EPA (Environmental Protection Agency) decided to adopt the same requirements. OBD II has now become the standard. The outcome of this is that malfunction codes have been standardized, and now the following systems are constantly monitored: catalyst performance, engine misfires, airflow from the evaporative system, and response rate of oxygen sensors. There are more controls than before, and they provide more efficiency. The indicator light must come on as soon as the vehicle goes over 1.5 times government standards, and if it starts flashing it means your catalyst is nearing possible breakdown. So this malfunction lamp is probably going to come on more often than before.
Prevention is better than the cure
The main purpose of the "Check Engine" warning is to protect the engine, the air quality of our planet, and ourselves. If those problems related to the "Check Engine" light are not looked at as soon as possible, other costly problems could occur.
Let's say for instance that one of the cylinders operates without sparks: the unburned gasoline will cause premature wearing of the piston by diluting the thin oil film on the cylinder wall necessary for proper lubrication. Also, this unburned fuel will ignite inside the catalyst and raise its temperature thus causing irreversible damages. A minor cause of warning would be an improperly tightened gas cap. In this case, OBD II would detect gas fumes leaking out of the fuel tank. More than a hundred malfunction codes may turn on that warning light.
But if problems are properly identified and quickly fixed, your vehicle will produce less emissions, your engine will have a better performance, and you'll save on gas.
In some instances, the replacement of emission control parts are guaranteed beyond the manufacturer's standard time period. The catalyst in your 1998 Chrysler Caravan being guaranteed for 8 years or 130,000 km is a good example. So remember to check your manufacturer's guarantee on those emission control parts.
You should know that the on-board computer keeps a record of the time the indicator light went on. That way, if you forget to make any needed repair on your vehicle, and your carelessness causes some important damages, your guarantee could be voided.
What To Do?
Porper maintenance will certainly avoid many problems. If your "Check Engine" light is on when everything seems to go fine, it's probably telling you something ! There's very little chance of your car breaking down on the spot but you shouldn't wait to bring it in for a qualified inspection. If you get a flash warning, it is recommended you move over and stop your vehicle, and then call for road-side assistance. Both your car and your wallet will be grateful.