Mystery Behind the 'Check Engine' Light
January 17, 2003
By JIM MOTAVALLI
It's a tiny rectangle hidden among the gauges clustered on
the dashboard near the steering wheel. When all is well, it
is blank and quiescent. But then one day, unaccountably, it
glows yellow and commands, "Check engine."
Drivers are trained to respond to orders of this sort. When
a light flashes "Low fuel," they hurry to a gas station.
When a tiny indicator speaks of inadequate oil pressure,
they add oil. But "Check engine"? Especially when, as is
usually the case, the engine shows no obvious signs of
doing anything but humming along contentedly?
How to check it? And what to check?
All cars sold in
America since 1996 are equipped with a new generation of
check-engine lights, but America doesn't seem to know why.
Respondents to a small and unscientific e-mail and
telephone survey are representative of what appears to be
national confusion about the meaning of the check-engine
light.
"Aargh," wrote Carl Frankel, a computer consultant from
Kingston, N.Y. "I haven't a clue! The shame, the horror."
Jennifer Kaylin, a freelance writer who lives in New Haven,
said: "I don't have the faintest idea what the check-engine
light means. I guess you should slam on the brakes, pull
over and dial a service station."
Mary Witkowski, a librarian in Connecticut, believes
strongly that the check-engine light signals a blown fuse,
but only in Hondas. "Two other people I know with Hondas
have had the same experience," she wrote.
A retired Kentucky banker named Bob Stoess sees a message
of approaching misfortune clear enough to serve as a
metaphor: "Let God be your check-engine light," he wrote on
the inspirational Web site Hangtough .com. "We need a light
to come on in our minds to help us avert conflict, pain or
disaster."
Valerie Richardson of Bridgeport, Conn., a graphic
designer, remembered panicking when the light appeared. "I
thought it meant the engine would be ruined forever if I
drove another foot," she said.
But as many drivers know, it wouldn't have been. After the
fear and panic of the light's first flash, the driver who
doesn't rush to a dealer usually notices as the days pass
that nothing at all seems to be awry.
As it happens, that isn't really true. The light may mean
many things. One frequent problem, for example, is that the
emissions system is off kilter, and the car is polluting
the air; another is that the gasoline cap is loose, causing
the car's computer to detect an unusual pressure level in
the tank (tighten it and the light will eventually go off).
But the glitches that activate the check-engine light are
often nothing a driver would readily notice. As a result,
the country is full of people driving around with
check-engine lights aglow - often while trying to figure
out how to shut them off.
A cottage industry has grown up around that shut-off
problem. Some mechanics advertise, "Check-engine lights
disconnected." Online marketers hawk $200 reset tools. And
Charlotte Kidd, a horticulture writer in Philadelphia, is
probably not alone in her solution: she keeps the glowing
check-engine light in her 1988 Subaru covered with a piece
of black tape.
The check-engine light, formally known as a malfunction
indicator lamp, is an indication of a failure somewhere,
and the problem is often emissions related. If the
catalytic converter or oxygen sensor is defective, the
level of pollutants coming from the tailpipe may have
soared.
Your car's computer is constantly checking information from
engine and transmission sensors against data stored in its
memory. When one of hundreds of potential faults is found,
the check-engine light comes on, and the computer records a
trouble code that can only be read with the right high-tech
tools - expensive computerized diagnostic equipment. This
system favors the service departments of auto dealerships,
often the only places in town where those tools can be
found.
Bob Frankston, a computer engineer and a creator of the
VisiCalc spreadsheet program renowned as the first "killer
app" software, felt helpless when his check-engine light
came on. "I was annoyed at what I consider the simple
refusal to share information with me," he wrote in an
e-mail message recently. "It's like replacing a temperature
gauge with an idiot light."
Mr. Frankston said he was tempted to buy an analyzing tool
or a software package that would let him plug into the port
where the coded messages can be retrieved and then read
them on his own computer. "But what good would it do me to
know that the Frobnitzer level is 17 percent?" he asked.
The frustration is shared by many auto mechanics. While
theoretically any mechanic can retrieve data from the car's
computer, the independent shop's life is made harder by
lack of access to service manuals, bulletins and diagnostic
equipment that are proprietary to manufacturer-approved
dealerships.
When the check-engine light came on one Sunday morning in
the 1997 Mazda MX6 owned by Trish Riley, an environmental
writer in Florida, she scrapped a planned drive to West
Palm Beach and consulted her owner's manual, which she said
offered only an ominous instruction: "See dealer
immediately." On Monday morning Ms. Riley's mechanic gave
her some advice that most definitely is not
manufacturer-approved. "He told me to disconnect the
battery cables, then reconnect them," she said. "And the
light hasn't been on since." (The electrical disconnection
erases the computer's memory - definitely not what the
federal government had in mind when it required the
installation of check-engine lights.)
Car owners' growing tendency not to take the check-engine
light seriously and auto mechanics' acts of sabotage to
disable it are both predictable responses to car computers'
mystifying messages. But since emissions problems are so
often what makes the light come on, one result is that a
lot of cars are now doing a lot of polluting. This has not
escaped notice in California, where the fight against air
pollution is constant. A 2001 state law requires that
carmakers make emissions-related service information
available to all approved mechanics.
Cars sold in the United States after 1996 have standardized
software called OBD-II (for on-board diagnostics) to
identify problems and switch on check-engine lights. But
carmakers use four different computer protocols for
retrieving data from car computers. And studies have shown
that OBD-II makes mistakes.
An alternative? There are hand-held OBD-II scan tools that
give some information and turn the light off, but they are
expensive and not for the average driver.
Carmakers could replace the cryptic "Check engine" message
with a specific readout. For example: "Bad heated oxygen
sensor. Estimated cost of repair $200 to $400. O.K. to
drive the car for a few days until you can get to a repair
shop." But they show no inclination to do so.
Mr. Frankston, the programming expert, isn't willing to
wait. He said he would rather see a digital interface that
made information available to amateurs who could design
their own systems for analyzing the computer data. But many
people still have trouble programming VCR's, let alone
designing software for analyzing engine problems.
The next time the check-engine light comes on, they will
probably just reach for the black tape.
Copyright 2002 The New York Times Company. |
