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TomcoTechtips
How to read trouble codes on Ford's EEC-III
The EEC-III is one of the
engine control computer systems
used by Ford since midyear 1978.
(We will cover the others in later
issues.) This procedure uses an
inexpensive voltmeter and other
generally available test devices
instead of the special diagnostic
tester originally specified by Ford.
Just follow these steps to get the
service codes from cars using this
system.
1. Connect the negative lead
from an analog (pointer type) voltme-
ter to the green thermactor air bypass
diverter (TAB/TAD) solenoid. (Fig. A)
This is usually found on the passen-
ger side of the carburetor. (Don't
confuse this with the EGR valve and
throttle kicker solenoids which are
usually found on the driver side of the
carburetor.)
2. Connect the positive lead
to the positive battery post.
3. Set the voltmeter to the
12v battery post.
4. Connect a 12v test light to
the canister purge ground circuit.
Caution: This is not the
bowl vent solenoid.
5. Start the engine and run it
at 2000 rpm for approximately one
minute. Then return to idle.
6. Apply 20" Hg vacuum to
the barometric pressure/manifold
absolute pressure (BP/MAP) sensor
vent port for eight seconds. Then
release the vacuum. (Fig. B)
The throttle kicker (TKS)
plunger will move rapidly in and out
to signal that the self test has begun.
Then it will remain out for approxi-
mately 1
1/2
minutes, signaling that the
system is in its diagnostic routine.
Finally it will return to curb idle and
the system will begin to give service
codes.
7. To read the service codes,
watch the pointer on the voltmeter.
Codes are displayed as needle
sweeps. (Example: 3 sweeps, pause,
1 sweep equals code 31). The
voltmeter needle will continue to
sweep until all codes in the memory
have been displayed. Then the 12v
test light you connected earlier will
come on signaling the end of the test.
Next, the computer will
energize the trottle kicker which will
raise the rpm to 1500 for 15 to 20
seconds, then return to idle. If you are
not sure of thew codes, repeat the test.
The following chart lists the service
codes and the components or circuits
they indicate for Ford's EEC-III. Keep in
mind, this is a condensed, basic service
code chart. This procedures much
handier than searching through large
service manuals. However, for specific
information, check the service manual for
the model and year of the car.
Service
Code
Instruction
11
VIP Test "Pass Status"
12
Engine RPM Out-of-Spec
21
Engine coolant temperature sensor
shorted, open or out of range
22
Manifold absolute pressure sensor
shorted or open
23
Throttle position sensor shorted, open
or out of range
24
Air charge temperature sensor
shorted, open or out of range
31
EGR valve inoperative
32
EGR valve position sensor shorted,
open or out of range
41
Fuel control system always lean
42
Fuel control system always rich
43
Engine coolant temperature-VTC3;
cold VIP test
44
Secondary Air system inoperative
EEC-III
SERVICE CODE CHART
THERMACTOR
AIR DIVERTER
(TAD) SOLENOID
THERMACTOR
AIR BYPASS
(TAB) SOLENOID
(Fig.A)
Green Wire
Analog Meter
Battery
(Fig.B) How to test for
open/closed loop status
and rich/lean exhaust
condition on
GM cars.
This sample tests tells you if the
engine is running in the open or
closed loop status, and also indicates
whether its exhaust condition is rich
or lean. It requires no special
equipment. GM describes this test as
placing the computer into the field
service mode.
First, with the ignition off, jump
the A and B terminals of the assembly
line connecting link (ALCL). (As you
may remember from the last issue,
this was accomplished using a
jumper tool or bent paper clip.
However, in that test we turned the
ignition on, but did not start the
engine). To perform this test, you will
start the engine and observe the
CHECK ENGINE or SERVICE
ENGINE SOON light
OPEN/CLOSED LOOP TEST
The SERVICE ENGINE
SOON light will begin to flash. Count
the number of flashes per second . A
rate of two and a half flashes per
second indicates the system is in
open loop operation. The system will
always be in open loop when first
started.
Once the engine coolant
reaches operating temperature and
the O2 sensor output voltage begins
to vary, the system enters closed loop
operation.
If the system fails to go into
closed loop operation, this indicates
that the engine coolant temperature
sensor may not be functioning
properly. Both should be checked
and replaced with a new Tomco, Inc.
unit if necessary.
RICH/LEAN FUEL MIXTURE TEST
The O2 sensor monitors the
status of the air/fuel ratio in the
exhaust. This status is indicated in the
way the SERVICE ENGINE SOON light
flashes.
At this point, the light is
flashing about one time per second. If
the flashes are short, so that the light
appears to be OFF more than ON, you
are reading a lean mixture. If the
flashes are long, so that the light
appears to be ON more than OFF, you
are reading a rich mixture.
DIAGNOSTIC CIRCUIT CHECK
ALCL CONNECTOR
(Look for letters on the ALCL terminals)
1 second
1 second
1 second
Check
Engine
Check
Engine
Check
Engine
Check
Engine
Check
Engine
(flash)
(flash)
(flash)
(flash)
(flash)
2-1/2 flashes per second=open loop
1 flash per second=closed loop Two new service aids for
GM computer-controlled carbs.
How to repair GM carburetors
with stripped lean mixture
adjustment screw threads.
This repair kit can save your
customer $600 to $800 for a new
carburetor. Tomco, Inc. offers a repair
kit with everything you need to repair
the lean mixture screw threads in the
bowl casting of four barrel Quadrajet
or two barrel Dual Jet computer-
controlled carburetors.
Here's how it works. First,
remove the mixture control solenoid
and all components, float and pin
assembly. Then place the carburetor
or fuel bowl on a firm base, making
sure the linkage is clear.
Now apply Locitte 271
(included in the kit) to the knurled
section of the repair stud. Place the
driving tool over the threaded shank
of the stud. Put the knurled end of the
stud in the counter bore of the
adjustment stud screw hole and drive
it into the hole and drive it into the
hole until the shoulder seats against
the casting.
Replace all components and
make the necessary adjustments . A
new spring and adjusting cap are
included in the kit, as are complete
instructions.
Now you can make "on the
bench" mixture adjustments to
GM carburetors.
This handy tool kit allows
you to adjust the lean mixture screw,
rich stop screw, and idle air bleed
valve on GM computer-controlled
Quadrajet and Dual Jet carburetors.
These adjustments must be made for
correct carburetor function. The
wrench is also needed for the final
on-the car mixture control solenoid
"dwell" setting.
The kit contains a lean
mixture gauge, a lean mixture screw
adjustment wrenchand a plunger
travel gauge for making the rich stop
screw adjustment. The kit also
contains complete instructions.
Both kits are available from
your local Tomco, Inc. jobber. Order
No. 13725 adjustment tool kit and No.
13726 repair kit.
Adjusting
Cap
Complete installation
instructions are included
with each kit.
Solenoid
Spring
Spring
Stud
Driving
Tool
Repair Stud
Apply
Loctite
Carburetor Body
This lit saves the expense of a
new 4 barrel Quadrajet or 2 barrel
Dual Jet computer controlled
(CCC) carburetor when the
threads for the lean mixture
adjusting screw in the bowl
casting strip out. A knurled
repair stud and adjusting cap
replace the original adjusting
screw.
LEAN MIXTURE SCREW REPAIR KIT #13726
GM computer controlled
Quadrajet and Dual Jet
carburetors require these