The Check Engine light can signal a number of different conditions which
indicate operating conditions not condoned by the manufacturere.

In many cases, a sensor will deteriorate, and the light will come on.  It
may
not mean instant disaster, but it signals a condition which needs to be
addressed.

Read the codes stored in the OBD system.  Then work toward a solution.

It can signal a variety of potential problems.  On many cars if the gas
cap isn't screwed down tight the air leak will trigger the check engine
light.  Since the light has been glowing continuosly for two weeks now,
I would get it in to a dealer pronto to have the error codes read and
the problem corrected.

Like they say, the light is turned on by the car's computer. It's just an
indicator that some computer reading isn't right. You have to consult the
computer to find out what it's complaining about. To do that you have to
plug in a device which can display the code or codes stored in the
computer's memory. Then you have to look up the code or codes in a manual
(or possibly somewhere on the Internet) to see what they mean. I have a
Haynes manual for my car which lists the computer codes and what they
mean.

You used to be able to read the codes by getting the computer to flash the
check engine light and count the numer of flashes. On some cars you could
connect an (analog) volt meter and count the number of ocillations of the
needle. I don't think any newer cars can do that. You have to have the
plugin display. My car is old enough that it does both the flashy and
wavy things, athough the light has only come on once.

On some cars there's a way to turn off the check engine light if it bother
you. I think on all cars disconnecting the batter under the hood will
erase the computer's memory and that turns off the check engine light. But
in both cases it's probably only for a short time because a persistent
problem will keep turning on the check engine light.

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William R Watt    National Capital FreeNet    Ottawa's free community network
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Last time I had a check engine light come on, it was from a faulty
crankshaft position sensor.  But it could be caused by any number of engine
"faults"

which word don't you understand?

It may "run fine" but the computer has detected a fault in the system
somewhere. The year of the vehicle makes a difference on what the
computer monitors. On pre 95 vehicles with OBDI it monitors a throttle
position sensor, ignition module, MAF or MAP sensor, O2 sensor, fuel
injection system, transmission shifting and pressure, electrical system
output, and a few dozen other items. ANY of them can generate a fault
and activate the light.
On newer vehicles you can add in MANY more sensors and even tighter
control. If the light is on you have a problem, you may not think so but
you do. You need to either have the codes read and do the repair
yourself OR take it to a shop and have them repair it.

As far as vehicles that have the check engine light on just because of
age, NOT true. That light is on because of a problem that those people
just don't bother to repair because "It runs fine and I have a feeling
it's just the light itself that's broken".  In some states that light
being on is an automatic failure on the safety inspection, so it becomes
either repair it or park it.