7
OFF
AUDIO
ON
CP9015 – Ford, Lincoln & Mercury
Domestic 1981& Newer
TM
®
ST0
HOLD
S
EL
F
TES
T OU
TP
U
T
1
2
3
Scanner Basics
When Do You Use it and What Does it Do?
When to Use the Code Scanner
Use the Code Scanner:
• When you experience a driveability
problem with your vehicle.
• When the “Check Engine” light comes
on (if used on vehicle).
• For a routine system check – even on
vehicles with a “Check Engine” light.
What the Code Scanner Does
The Code Scanner makes the vehicle
computer run special tests to check out
various parts of the system. The Code
Scanner plugs into vehicle wiring which
connects directly into two engine
computer circuits. One circuit is called
Self-Test Input (STI). The Code Scanner
uses this wire to tell the computer to run
the tests. The other circuit is called Self-
Test Output (STO).
The computer sends test results back to
the Code Scanner by using a pulse type
signal on this wire.
T
M
TEST
HOLD
CP
9015 - Ford, Lincoln & Mercury
AUDIO
ON
OFF
Code Scanner Controls
1 HOLD/TEST switch
This switch connects to the computer’s
Self-Test Input (STI) circuit.
• HOLD – The STI wire is unconnected.
(Normal position – no testing.)
• TEST – The STI wire is connected to
vehicle ground. (Computer starts
testing procedure.)
2 SELF-TEST OUTPUT light
This light is connected to the STO circuit
coming from the computer.
• Light OFF – The STO signal is “high”
(about 5 volts present).
• Light ON – The STO signal is “low”
(near zero volts).
A pulse type signal on the STO wire will
cause this light to blink. This is how the
computer sends test results to the Code
Scanner. See Section 4 or 7 for details.
Note: With the Code Scanner con-
nected and ignition key OFF, the light
may be ON or OFF – depends upon
vehicle. This does not affect testing
performance.
3 AUDIO switch
• Switch ON – A tone sounds whenever
the Self-Test Output light is lit.
• Switch OFF – Tone is always OFF.
This feature is useful when the STO light
can not be easily seen, such as when
performing the “wiggle” test described in
Section 6.
Note: With the Code Scanner con-
nected, Audio switch ON and ignition key
OFF, the tone may be ON or OFF (no
matter what the light does) – depends
upon vehicle. This does not affect testing
performance.
