Unfortunately, the majority of recurrent Check Engine episodes eventually lead to some professional repair time. The most common problems that trigger the light are emission control malfunctions. The emission control system is what your car uses to try to keep our air a little cleaner. To do this, it employs dozens of sensors, valves, flaps, heated wires and probably some fairy dust. Every car made in the last 20 years has at least one oxygen sensor (we saw a Toyota that had four of them recently), and they don't last forever. If they go, expect around $300 per sensor in replacement costs.
But don't throw your wallet in the street just yet. There are also plenty of little things that can make the Check Engine light come on, and many are easily corrected. Here are a few of the more commonly occurring issues:
Your gas cap isn't on tight enough.
You read that right, it might be your gas
cap. Some cars measure how much pressure
is building up inside your gas tank. It
involves a series of mathematical algorithms
that track your driving style and how much
pressure is usually in the tank, then set
off an alarm if it strays a certain percentage
from the average. Whatever. All is means
is that if you're gas cap isn't on tight,
it thinks something is up and lights the
orange dashboard candle, the Check Engine
light. Tighten the gas cap and see what
happens. It may take a week or more before
the light goes out.
Your engine got wet where it didn't
like it
Any electrical burp under the hood can cause
one of your car's gazillion sensors to
take a funny reading. When it does, you
can expect to see the Check Engine light.
We worked on a Ford truck once that triggered
the Check Engine light every time it rained.
After a lot of diagnosis, we found water
that was dripping onto a spark plug wire,
then running down the wire to the engine's
head, causing an occasional short. Every
time the water ran down the wire, the light
came on. A few days later, it would turn
off on its own. Be sure your engine doesn't
have a wetness problem. More common than
rain water getting in there is the overzealous
owner who sprays his engine down at the
high pressure car wash, shooting water into
every crevice of the engine, thus lighting
the light.
Your spark plug wires are bad
As your spark plug wires start to get old,
they may develop tiny cracks which can let
little bursts of electricity out. This electricity
was supposed to be going to a spark plug,
and since it didn't, the engine will misfire
slightly, meaning one of the spark plugs
didn't spark enough. Once again, this
can cause the Check Engine light to come
on. With your engine off, check your spark
plug wires for tiny cracks or holes, especially
around the ends of the wires. If they look
shabby, you should replace them.
