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The computer system in today's vehicles
does more than control engine operation - it
can help you find problems, too! Special
testing abilities are permanently pro-
grammed into the computer by factory
engineers. These tests check the compo-
nents connected to the computer which are
used for (typically): fuel delivery, idle speed
control, spark timing and emission systems.
Mechanics have used these tests for years.
Now you can do the same thing by using
the Actron Code Scanner!
The engine computer runs the special
tests. The type of testing varies with
manufacturer, engine, model year etc.
There is no "universal" test that is the same
for all vehicles. The tests examine INPUTS
(electrical signals going INTO the
computer) and OUTPUTS (electrical
signals coming OUT of the computer).
Input signals which have "wrong" values or
output circuits which don't behave correctly
are noted by the test program and the
results are stored in the computer's
memory. These tests are important. The
computer can not control the engine
properly if it has bad inputs or outputs!
The test results are stored by using code
numbers, usually called "trouble codes"
or "diagnostic codes." For example, a
code 23 might mean "throttle position
sensor signal voltage is incorrect." Code
meanings are listed in Sections 6, 9 and
12. Specific code definitions vary with
manufacturer, engine and model year, so
you may want to refer to a vehicle
service manual for additional informa-
tion. These manuals are available from
the manufacturer, other publishers or
your local public library. (See manual
listing on page 4.)
You obtain trouble codes from the engine
computer memory by using the Actron
Code Scanner tool. Refer to section 5, 8
or 11 for details. After you get the trouble
codes, you can either:
• Have your vehicle professionally
serviced. Trouble codes indicate
problems found by the computer.
or,
• Repair the vehicle yourself using trouble
codes to help pinpoint the problem.
To find the cause of the problem yourself,
you need to perform special test
procedures called "diagnostics". These
procedures are in the vehicle service
manual. There are many possible causes
for any problem. For example, suppose
you turned on a wall switch in your home
and the ceiling light did not turn on. Is it a
bad bulb or light socket? Is the bulb
installed correctly? Are there problems
with the wiring or wall switch? Maybe
there is no power coming into the house!
As you can see, there are many possible
causes. The diagnostics written for
servicing a particular trouble code take
into account all the possibilities. If you
follow these procedures, you should be
able to find the problem causing the code
and fix it if you want to "do-it-yourself."
Using the Actron Code Scanner to
obtain trouble codes is fast and easy.
Trouble codes give you valuable
knowledge – whether you go for
professional vehicle servicing or "do-it-
yourself." Now that you know what
trouble codes are and where they come
from, you are well on your way to fixing
today's computer controlled vehicles!
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