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Engine Check
Don't hit the panic button, but don't disregard it, either.
By Joe Gutierrez
It's a small rectangle hidden among the gauges clustered on the instrument
panel behind the steering wheel. It flashes briefly when you turn the ignition
on—along with other system checks like anti-lock brakes—to let you know the
system is ready to perform its prescribed job.
After briefly flashing at start-up indicating all is well, it is blank and
dormant as you drive happily on your way. Then one day, inexplicably, it glows
yellow and warns, "Check Engine."
What do you check and why? The engine shows no obvious signs of anything
except running down the road in quite contentment.
The Environmental Protection Agency and the California Air Resources Board
established regulations requiring on-board diagnostics systems on cars and
light-duty trucks (pickups, vans and SUVs) beginning with the 1994 model year.
All '96 and newer cars and trucks have a powerful computer which uses
second-generation on-board diagnostics, or OBDII, technology.
The purpose of the OBDII system is to ensure proper emission-control system
operation for the vehicle's lifetime by monitoring emission related components
and systems for deterioration and malfunction.
When the OBDII system determines that an emission problem exists, the
computer illuminates the dashboard light indicating "Service Engine
Soon" or "Check Engine" or displays an engine symbol. This light,
usually yellow in color, serves to inform the driver that a problem has been
detected and vehicle service is needed.
Warning Signs
OBDII assesses engine misfire situations,
the most severe of which indicates the possibility that the catalytic converter
is in danger of overheating. When this occurs, the yellow "check
engine" light will blink on and off.
Don't hit the panic button and stop the car when the yellow message starts
flashing. However, it is important to reduce the speed of the vehicle. The
vehicle should not be driven long distances with the light flashing.
The system is also continuously checking information from the engine and
transmission sensors against data stored in its memory. When one of hundreds of
faults is found, the check engine light comes on and stays on. This can mean
many things, from an oxygen sensor malfunction to a fouled spark plug.
The continuous light tells the driver that something is amiss, and to bring
the vehicle in for service. This is not an emergency situation and it isn't
necessary to immediately bring the car to the dealership. However, don't drive
for more than a few days with the light on.
A not uncommon cause for the light to illuminate is a loose gas cap. Check to
make sure it is tightened properly, and if that's the cause, the dashboard light
will go out after several trips.
If the problem that caused the light to come on disappears after a few trips—
perhaps a fouled spark plug has cleared—the OBDII computer will turn the light
off. This is not an indication of a faulty system. In fact, the system is doing
its job to verify that a problem existed and was caused by a temporary problem,
which has gone away. Your car needs no special attention unless the light comes
on again.
The glitches that activate the "check engine" light are often
nothing a driver can readily detect, but that doesn't mean everything is working
properly. There can be a condition that wastes fuel, shortens engine life or
could lead to expensive repairs if left unaddressed. And, since the condition is
usually emission related, the level of pollutants coming from the tailpipe can
soar.
So, if the check engine light comes on, don't hit the panic button, but don't
disregard it, either.
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