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The
Computer in your 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.
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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