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What's All This
About a
Computer
in My Car?
by MIKE EMERY
The
"Computer" in Your Car Doesn't Have a Screen,
a keyboard, or a Disk Drive --- but It's Got Lots of
Connections.
Your car's on-board
computer doesn't look anything like the kind that's used
on a desktop. The "computer" is a small box
called an ECM (Electronic Control Module), often mounted
behind the glove box or in the engine compartment. The
ECM controls all the essentials of engine operation:
spark timing, fuel delivery, emissions, and in some
cases even the air conditioning or the automatic
transmission. Keeping all those systems in tip-top shape
is no simple job; it requires complex test equipment and
advanced diagnostic skills.
The computer
continuously receives electrical signals from sensors
and input devices, located in and around the engine. It
analyzes this information and sends a stream of control
signals to valves, controllers and other output devices,
to balance the requirements of power, fuel economy and
emission control. Some of the most common devices are
shown in this brochure. Every engine, every car and
every computer system is different -- but all the
sensors, all the output devices, must be in perfect
"sync" for the car to run properly.
No system is
foolproof. When problems develop, the
malfunctioning parts must be replaced or adjusted. Otherwise the car won't run
right, the gas mileage will be poor, and the car won't
pass an emissions inspection. Only a qualified
technician, with the right diagnostic equipment and
technical data, can find out what's wrong and restore
your car to original performance specifications.
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Watch For These Warning Signs That Tell You
Your Vehicle Needs Service
- "Check
Engine" or "Service Engine" light on
- "Rotten
egg" smell from the exhaust
- Rough running or
stalling
- Engine knocking or
pinging
- Unstable, surging,
or high idle
- Lack of power
- Poor gas mileage
- Engine runs on
after turning key off
The Professional
Difference
The old-fashioned
tune-up used to be done "by ear", but this
isn't possible with computer-controlled engines A
complete diagnostic check, followed by professional
service, should be performed at factory-recommended
intervals, or whenever your car shows any of the above
warning signs. Our expert technicians can:
- Test idle speed,
throttle response, engine temperature, fuel system
pressure, manifold vacuum, exhaust emission levels
- Tap in and read the
signals being sent between the computer, its
sensors, and the output devices
- Retrieve and
investigate any "trouble codes" stored in
the engine's computer, indicating that something is
wrong or out of spec.
- Repair or replace
any malfunctioning parts; perform scheduled
replacements or service as recommended by car
manufacturer
- Restore your car to
original performance specifications, reliability and
emission control requirements
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