It's just a little amber lamp in the dashboard, a tiny bulb
behind a plastic pane the size of a postage stamp, inscribed with a
very big message.
Depending on the car's make and model, it might say ``CHECK
ENGINE,'' as if you possessed the ability to pry open the hood and
make a snap diagnosis. Others say ``SERVICE ENGINE SOON,'' worded
just vaguely enough to enable us procrastinators.
No matter how it's communicated, the effect can be unnerving. Who
knows what evil lurks in the hearts of engines? Only the computer
But unravelling the mystery of the enigmatic little lamp is
considerably easier - and usually less painful - than most people
think. While there's little reason to shut the vehicle off and
sprint for the nearest mechanic, the light shouldn't be ignored for
``It's your car's way of telling you, 'You might be meeting Larry
the tow-truck guy soon,''' says Bill Jaap, owner of Good Carma VW
and Audi Repair in Minneapolis. ``It's a warning, and it can be
menacing. Even though the car still runs well, I think it's a good
idea to bring it in.''
WHAT IT IS:
The lamp's formal name is the malfunction indication light, or
Today's cars are equipped with dozens of sensors and a computer
that make on-the-fly adjustments to maximize fuel efficiency and
minimize carbon emissions. If a sensor detects something amiss, it
sends a code to the computer, and voila: ``CHECK ENGINE.''
That code is stored in the computer - and the light stays on -
until it's retrieved. And that part is surprisingly simple: It's
just a matter of plugging a handheld gadget into a connector that's
usually located beneath the steering column.
WHAT NOT TO DO:
Panic. Unless your car is idling rough, starting hard, hesitating
or smoking, it's OK to keep driving when the light comes on. (In a
few models, the light will flash or turn red if the problem is
serious. If this happens, DO pull over asap.)
But it's unwise to ignore it. For one thing, the problem will
likely mean a failed emissions inspection down the line. For
another, many of these small, undetectable problems can cause costly
engine damage if left untreated.
``It's kind of a false signal to some people who maybe have been
driving around with it on for a year,'' Jaap says. ``Even though the
problem can be very slight, my opinion is that you shouldn't get
desensitized to it. It's on for a reason.''
Tip: Don't pay a mechanic to read the code unless the shop offers
to credit the money back in related repairs. The service is easy
enough to get for free.
WHAT TO DO:
Obviously, if the car is under warranty, take it to the dealer.
But with older cars, many mechanics and auto-parts stores will
retrieve the code gratis.
Do-it-yourselfers can purchase code readers for $50 to $200, and
some software programs will turn your laptop into a scan tool with a
special connector. Some readers give a number that needs to be
cross-referenced; more expensive scanners will display details.
But this is where a little knowledge can be a dangerous thing,
Jaap cautions. The readings are often vague, and won't necessarily
tell you what needs doing.
``It can be even more expensive to try and guess what's going to
fix it, just based on what a scan at an auto-parts store tells
you,'' Jaap says. ``That's kind of hearsay and conjecture, and I'd
go broke if I did that.''
At the very least, the code can help you (or your mechanic)
decide whether it's something that can be put off for a bit.
WHY ALL THE RIGMAROLE? CAN'T MY CAR JUST TELL ME WHAT'S WRONG?
Said Deep, a spokesman for Ford Motor Co., says indicators on
modern cars are getting more sophisticated, telling drivers, for
instance, how close they are to needing an oil change, or when a
tire is getting low.
``But there's a limited amount of real estate on the instrument
panel,'' Deep says, ``and there's a certain amount of information
overload that we want to avoid.''
Carmakers are only adding messages that drivers are comfortable
dealing with - specific messages for a headlight out, say, or low
``When we get into computer operations, like delicate air/gas
mixture issues or the way your transmission shifts, that's something
we think is more suited for a trained mechanic with the proper
equipment,'' Deep says.
SO WHAT'S THE LIGHT SAYING?
The computer can detect scores of possible problems, ranging from
silly to sinister. As often as not, the MIL comes on when the gas
cap isn't screwed on tight enough or the oil dipstick isn't pushed
in all the way.
But let's say the computer indicates a malfunctioning oxygen
sensor, an often troublesome doodad that measures the amount of
oxygen in your exhaust. Without its feedback, the engine will surely
start, run and seem to perform normally. Fuel economy may dip a bit,
though you'll hardly notice. Why bother with a costly repair?
Because when it comes time to pass an emissions inspection,
forget it. If the exhaust coming out of your tailpipe isn't just so,
no licence plate for you.
At its core, that's really what gave rise to the MIL in the first
HOW IT GOT SO COMPLICATED:
Before the 1980s, the dashboard gave gearheads all the vital
signs they needed to keep moving down the road: fuel level, oil
pressure, temperature, RPMs and, in some cases, alternator voltage.
But these dials revealed nothing about the intricate balances of
fuel mixture or carbon emissions. As smog became a political issue
in the early 1980s, the U.S. government intervened with emissions
control standards. Making a car perform up to snuff got a lot more
There are endless ways our cars can run afoul of these standards;
without sensors to point the way, mechanics would spend more time
diagnosing than fixing. And other than an annual emissions
inspection, how would Earth-friendly drivers know their vehicle was
an environmental menace?
In that vein, perhaps it's only fair to think of the MIL as your
friend - the automotive equivalent of a canary in the coal mine.
``Older cars were simpler, but we've come a long way,'' Jaap
says. ``I have to say that it's really easier to diagnose the modern
engine - if you have the right tools. Its an all-around better