The mysterious "check engine" light

By: Jason Miller

If you have had your car or SUV long enough, that annoying
"check engine" light has probably made an appearance on your
dash board. The first time I saw it, I popped the hood and
"checked" the engine. It seemed ok to me. My car was running
fine. So like most experienced car drivers, I ignored it or I
tried too. The really insidious thing about that little innocent
light is that it really gets to you after a while. After a long
drive at night with that light shining at me like a laser beam,
I considered putting it out its misery with my tire iron. Which
brings up the question, what is it there for. Well here is a
basic answer. The "check engine" light is connected to the car's
engine fuel management computer. This is the computer that runs
the fuel injectors, reads the engine sensors, etc. The oxygen
sensors are used by the ECM to determine how accurately it's
injecting the fuel, and adjusting the way the fuel is injected
to compensate for changing conditions. When the computer inside
the ECM detects that there is something wrong, the ECM turns on
the "check engine" light. For example, a bad sensor or engine
operating parameter that exceeds a preprogrammed set point then
the ECM turns on the light to let you, the driver, know that
something is wrong and needs to be corrected. It doesn't mean
something cataclysmic is about to happen, just that the computer
that runs a lot of the functions in your engine is getting some
bad information. Most of the time this means an oxygen sensor
has failed and needs to be replaced. In a lot of states, your
car will not pass the inspection when the light is on. So you
have to fix it before you can get a new inspection sticker.

About the author:
Jason is the webmaster for Red Hill Supply - Online Air Tools

http://www.redhillsupply.com