Retrieving
EEC Diagnostic Codes
- by
Jeff Korn
Retrieving
the EEC diagnostic
codes can be done
with a Ford EEC IV
“flashing light”
code scanner
available at most
auto parts stores
for about $30 to
$40, but you can
retrieve the codes
without buying a
code scanner. This
can be done by using
a jumper wire and
your check engine
light, if your car
has one, or a jumper
wire and an analog
voltmeter or 12 Volt
Light Emitting Diode
(LED) available from
Radio Shack for
under $2. The least
desirable way to run
the test is to use a
voltmeter, as it can
be difficult to
count out the code
pulses by watching
the needle on the
meter swing. You can
also build a
dedicated code
scanner to run the
codes from inside
the car for under $5
in parts.
This code
scanner is described
in another tech
article here on the
NATO site.
The EEC diagnostic code scan consists of two different tests, called the Key On Engine Off (KOEO) and the Key On Engine Running (KOER) tests. The KOEO test consists of two different test sections. The first section will identify current faults, and the second section, called the continuous memory test, which gives stored codes for intermittent faults. After the KOEO codes are outputted, the EEC enters the output state test / wiggle test mode, which allows you to activate / deactivate all the EEC activators (IAB, EVR solenoid, etc), and look for intermittent wiring and sensor faults. The KOER test also enters the wiggle test mode after the codes have been outputted. The code scanner is connected in the same way for both the KOEO and KOER test.
Hooking
up the code scanner
Before
running any tests,
be sure the car has
been warmed to
operating
temperature.
If
you have a
commercial code
scanner, locate the
EEC TEST connector
and the single
terminal self test
input (STI)
connector under the
hood. On Turbo
Coupes, this
connector is at the
front of the drivers
side strut tower.
Plug in the code
scanner according to
the manufacturers
directions.
If
you want to use a
jumper wire and
analog voltmeter, or
jumper wire and 12
Volt LED, locate the
EEC TEST connector
and STI connector
under the hood.
Refer to the
figure below that
shows how to hook up
the jumper wire and
the 12 V LED.
If using an
analog voltmeter,
replace the LED with
the voltmeter.
Do not hook
up the jumper wire
yet!!
If your car has an operating check engine light (CEL), all you need is the jumper wire, and the CEL will flash out the codes.
With
the motor at
operating
temperature, turn
the key to the run.
Insert the jumper
wire.
You may hear
some clicking as
some relays operate
for a few seconds.
After a few seconds,
the two digit codes
will begin flashing
on the CEL or LED,
or if using a
voltmeter, the
needle will begin
swinging between
zero and 12 volts.
If the system passes
the current fault
test, it will flash
once for about ˝
second, and once for
˝ second one second
later. A few seconds
later, it will
repeat the “code
11”.
If the
current fault test
fails, it will flash
a code or codes for
the fault or faults.
For example, if the
EEC senses the
throttle position
sensor fault, it
will flash twice,
and then three times
(code 23) and then
repeat the code 23.
About
10 to 15 seconds
after the current
fault codes are
outputted, a single
flash will be seen.
This is
called the separator
pulse, and separates
the current fault
part of the test
from the continuous
memory intermittent
fault part of the
test.
About 10 to
15 seconds after the
separator flash, the
continuous memory
codes will be
outputted in the
same way as in the
current fault test.
These codes
indicate that the
EEC detected an
intermittent fault
in some system.
To erase the
continuous code
memory
codes, rerun
the KOEO test, and
disconnect the
jumper wire or
disconnect the STI
connector from the
commercial code
scanner while the
codes are being
outputted.
If
the scanner is left
hooked up for
roughly two minutes
after the last code
has been outputted,
the wiggle test mode
will become active.
In this test
mode, you can wiggle
the wiring harness,
tap on various
sensors, etc to look
for an intermittent
fault.
If an
intermittent fault
is detected, the
scanner will
momentarily light
up, and if the
intermittent fault
lasts long enough,
the EEC will store a
fault code in the
continuous memory.
The
activators can be
tested for operation
using the output
state test. After
the last code is
outputted, briefly
floor the gas pedal,
and then release.
The light on the
scanner will stay
lighted, and all the
activators will turn
on . Another
brief wide open
throttle will turn
off the light on the
scanner, and will
turn off all the
activators. This on
/ off process can be
repeated as many
times as needed.
If
you have the scanner
or jumper connected,
remove the jumper,
or disconnect the
STI from the
scanner.
Start the
car, and run it for
several minutes to
be sure the motor is
at operating
temperature, and to
warm the oxygen
sensor to operating
temperature. Insert
the jumper wire or
connect the code
scanner. The
motor will rev up,
idle down, and do
all sorts of strange
things.
Soon after
starting the test,
the engine ID code
will flash. This
code is ˝ the
number of cylinders,
so on a Turbo Coupe,
two flashes will be
seen.
After a
while, the idle will
settle down, and a
single flash will be
seen. This is the
Dynamic Response
Code.
When this
flash is seen, tap
the brake to
exercise BOO (Brake
on / off) circuit,
and do a brief wide
open throttle to
bring the RPM up to
3000 to 4000. This
tests the TPS and
the VAF (vane air
flow) meter. You
may also want to tap
on the intake
manifold with a
small hammer or
wrench to test the
knock sensor. If you
don’t tap on the
intake, a code 25
for the KS will
result.
Shortly after
the dynamic response
code, the KOER codes
will be outputted.
These codes
will each be
outputted twice,
just as in the KOEO
test.
If the scanner is left connected, roughly two minutes after the last code is outputted, the wiggle test mode will activate. You can wiggle the harness, tap sensors, etc. in the same way as in the KOEO test. Any fault codes will be stored in the continuous memory portion of the KOEO test.