Check Engine Light
Starting in 1996, all automobiles sold in the United States were mandated by the government to be equipped with On Board Diagnostics II (OBD-II). OBD-II is the protocol of the emissions system; however, it should be considered part of the operating parameters for the engine because it is part of the Digital Motor Electronics (DME) control unit.
Much like a scan tool, OBD-II constantly oversees and interrogates the engine, watching for any irregularity or change in operation that is impacting the engine’s emissions. Engine cylinder miss-fires, rich or lean running conditions, cold start operation and fuel tank pressure are just a few of OBD-II oversight responsibilities. Just about any sensor failure or engine operating system is monitored by OBD-II.
The Check Engine Light (CEL) is also known as the Malfunction Indicator Light (MIL) or Service Engine Soon Light. When illuminated, it provides a means of notification to the driver that there is a problem with the engine management or emission system. If you see a continuously illuminated CEL, the problem may be minor and you should be able to safely drive your car home and then to your place of service, but the problem should be diagnosed very soon to insure that no damage is taking place.
If the MIL or CEL is blinking, your OBD-II system has determined that a possible catalytic convertor damaging condition exists, and you should not drive your car. Turn the engine off immediately and have it towed to a service location where the problem can be diagnosed. This would be a better decision than risking further damage to your emission control system. The complete automobile emissions system is designed to protect the catalytic convertor(s) because it is what is responsible for reducing the exhaust emissions.
The internal combustion engine produces three main pollutants: CO, HC and NOx. CO (Carbon Monoxide) gets converted to CO2, which plants like. HC (Hydrocarbons) gets converted into H2O (water) — you’ve seen cars with water dripping from their tail pipe? The last and most critical pollutant is NOx (Oxides of Nitrogen). These get converted into N2 (Nitrogen), which is what most of our atmosphere consists of.
Reading fault codes can be a tricky and misleading situation when you do not have the proper diagnostic tools. An inexpensive OBD-II fault code reader is easily obtained from your local automotive parts store, but it could lead you in the wrong direction. It is always best to utilize the factory diagnostic system and a trained technician familiar with you car. Interrogate not just the engine management system but all the control units in your vehicle. Print and retain all the fault codes in every system for future reference.
Once your problem is repaired, the technician can utilize what is called the Mode Six (notated $06) data to confirm that your vehicle is repaired properly and a re-occurring check engine light will not be in your immediate future.
Tony Callas & Tom Prine