Actron GM Code Scanner CP9001 - Manual (Page 5)

5
About Codes
Where do they come from and what are they for?
Engine computers can find
problems.
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 programmed into the
computer by factory engineers. These
tests check the components 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 tool!
Engine computers perform special
tests.
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 IN to
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!
Code numbers give test results.
The test results are stored by using
code numbers, usually called “trouble
codes” or “diagnostic codes.” For
example, a code 22 might mean
“throttle position sensor signal voltage
is too low.” Code meanings are listed
in Section 4. Specific code definitions
vary with manufacturer, engine and
model year, so you may want to refer to
a vehicle service manual for additional
information. These manuals are
available from the manufacturer, other
publishers or your local public library.
(See Vehicle Service Info on page 4.)
Read Codes with the Code
Scanner.
You obtain trouble codes from the
engine computer memory by using the
Actron Code Scanner tool. Refer to
section 2 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.
Trouble Codes and Diagnostics
help you fix the problem.
To find the problem cause yourself, you
need 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 possibili-
ties. 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.”
Actron makes it easy to fix
computer vehicles
Using the Actron Code Scanner to
obtain trouble codes is fast and easy.