Possible Eec Troubles! Help!

Sep 19, 2016
19
5
13
Chicago, IL
#1
Hello! This is my first post on StangNet. I've done plenty of lurking and searching to find lots of helpful information, this place is amazing!
Before someone posts "Search it.", I have.

Please read on.

My car (1989 5.0 LX) has been having lots and lots of electrical issues. I've come to what I thought was the end of all my electrical work when I finally put in a new starter, as my stock one crapped out. I go to start the car, aaanndd...nothing. I didn't have spark anymore. My ignition switch (electrical) is new, the ignition coil is new, my starter solenoid is new, my distributer is new, my starter cable is new (the old was was corroded to all hell, welcome to the Midwest), and both my positive and negative battery cables are new. I replaced the starter cable with 6 gauge marine grade cable and my battery wires with 4 gauge marine grade wire. I have fuel and adequate fuel pressure (around 35-40 psi) while cranking and my starter is working wonderfully, I upgraded to a high torque starter. To begin diagnosing, I looked to see if my fuel injectors were receiving power and a signal from the distributer. All injectors had power, but no signal. I figured it could be my PIP sensor. Nope, I used a test light to probe the PIP wire coming out of the TFI module plug and it flashed as it should while cranking. Same for the SPOUT wire. I tested all of the wires coming out of the TFI module matter of fact. The dark blue wire (PIP) flashed as it should, the yellow/green wire (SPOUT) flashed as it should, both the red/blue wire and the red/green wire have power in either run or crank (accordingly), the dark green/yellow wire (IDM) had power coming out of it and was sending a signal, and the black/orange wire (IGN) is/has a good ground. I'm feeling this issue may be my EEC now. I did some testing with the EEC connector NOT connected to the EEC as it was easier to access the specific wires I wanted to test this way. All testing of the wires was done with the key in RUN. Pin 56 (PIP) was receiving a signal as it should be while cranking, Pin 36 (SPOUT) was receiving a signal as it should be while cranking, Pin 4 (IDM) was receiving power/signal, and Pin 16 (IGN Ground) is good. I also tested pin 20 (Case ground), pin 49 (HEGO ground), pin 40 (PWR ground), pin 60 (PWR ground), pin 22 (fuel pump), pin 37 (VPWR), pin 57 (VPWR), and pin 1 (KAPWR).
Pin 20 - GOOD
Pin 49 - GOOD
Pin 40 & 60 - GOOD
Pin 22 - DEAD. I've ran my own power wires to my fuel pump (relayed, fused, and switched of course) and I have had the car run with this setup before. I don't see this as being an issue. I had issues with my FP wiring in the past and decided to do this for simplicity.
Pin 37 & 57 - DEAD
Pin 1 - DEAD

I've removed my EEC to inspect it for damage. It smells fine (no burning scent) and I've even taken it apart to inspect the circuit board. I'm not a computer repairman, but it looked OK from what I could tell. I honestly wouldn't know though.
Do you think my EEC is dead or do I have more wiring issues? I'm frustrated and stumped. The car was running the other day and as soon as I finalized my wiring and put in a new starter the car decides to do this. I'm not wanting to invest into another EEC or looking to pay to have my EEC repaired until I KNOW it's dead.
I know this is quite a lengthy post, but I want to be as descriptive as possible for anyone that may be able to give a knowledgeable opinion on this.
THANK YOU for reading! Any and all replies are appreciated!
 
Last edited:
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Sep 19, 2016
19
5
13
Chicago, IL
#2
I'd also like to add that I did a self EEC check to see if I could pull any codes and I saw NO flashes. I have a check engine light with the EEC plugged in. My EEC is an A9P (Ford PN E9ZF-12A650-C2A).
 

karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
7,287
2,512
193
polk county florida
#3
Open the eec up and give us a shot of the board
Good description of what has been done.
If the computer is not going into test mode I would suspect it has a malfunction but that's just a guess,
Your testing was done from the cramks but no start checklist?
Someone smarter than me will chime in
 
Sep 19, 2016
19
5
13
Chicago, IL
#4
I'll snap some pics later and post them.
Thank you, I hope the description was adequate.
I did not use that checklist, but I've already gone over many of the steps on it with my own testing.
 
Sep 19, 2016
19
5
13
Chicago, IL
#5
In reference to this...
https://www.stangnet.com/mustang-fo...-checklist-for-fuel-injected-mustangs.787471/

No spark, possible failed items in order of their probability:
A) I do no have an ignition box.
B) My PIP sensor is functioning.
C) All wires coming out of my TFI module are functioning.
D) My coil is good.
E) My EEC relay is good. All circuits coming out of the EEC relay have power with the key in run.
F) I'll verify today if my computer was receiving power. I took my computer home (my car is at a shop), but I'll check to see if the pin that gives the computer power is getting power.
G) My ignition switch is good.
H) I've cleaned up this ground and I've made sure it's good.
I) That's what this post is about - verifying that my computer is dead.
J) I've checked this ground before with a test light and it seems fine. The ground strap itself looks okay as well. I'll clean up this ground today. I don't see this as being the reason of failure though, although I haven't cleaned it, it seems adequate.
K) I was having this issue in the past when the car was still firing. I fixed this issue - the car would run. The coil receives power as it should with the key in both run and while cranking.
 
Sep 19, 2016
19
5
13
Chicago, IL
#6
In reference to this...
https://www.stangnet.com/mustang-fo...-checklist-for-fuel-injected-mustangs.787471/

No spark, possible failed items in order of their probability:
A) I do not have an ignition box.
B) My PIP sensor is functioning.
C) All wires coming out of my TFI module are functioning.
D) My coil is good.
E) My EEC relay is good. All circuits coming out of the EEC relay have power with the key in run.
F) I'll verify today if my computer was receiving power. I took my computer home (my car is at a shop), but I'll check to see if the pin that gives the computer power is getting power.
G) My ignition switch is good.
H) I've cleaned up this ground and I've made sure it's good.
I) That's what this post is about - verifying that my computer is dead.
J) I've checked this ground before with a test light and it seems fine. The ground strap itself looks okay as well. I'll clean up this ground today. I don't see this as being the reason of failure though, although I haven't cleaned it, it seems adequate.
K) I was having this issue in the past when the car was still firing. I fixed this issue - the car would run. The coil receives power as it should with the key in both run and while cranking.
 
Sep 19, 2016
19
5
13
Chicago, IL
#8
Just tested all of the pins AT the EEC connector with the KOEO.

Pin 1 (KAPWR) - dead
Pin 2
Pin 3 (VSSDIF +) - dead
Pin 4 (IDM) - power
Pin 5
Pin 6 (VSSDIF -) - good
Pin 7 (ECT) - dead
Pin 8
Pin 9 (MAFRTN) - dead
Pin 10 (ACCS) - dead
Pin 11
Pin 12 (INJ 3) - dead
Pin 13 (INJ 4) - dead
Pin 14 (INJ 5) - dead
Pin 15 (INJ 6) - dead
Pin 16 (IGN GND) - good
Pin 17 (STO/MIL) - power
Pin 18
Pin 19 (FPM) - dead
Pin 20 (CASE GROUND) - good
Pin 21 (Idle speed control) - dead
Pin 22 (FP) - dead
Pin 23
Pin 24
Pin 25 (ACT) - dead
Pin 26 (VREF) - dead
Pin 27 (EVP) - dead
Pin 28
Pin 29 (HEGO R) - dead
Pin 30 (NDS) - dead
Pin 31 (CANP) - dead
Pin 32 (AM2) - dead
Pin 33 (EVR) - dead
Pin 34
Pin 35
Pin 36 (SPOUT) - power
Pin 37 (VPWR) - dead
Pin 38 (AM1) - dead
Pin 39
Pin 40 (PWR GND) - good
Pin 41
Pin 42 (INJ 7) - dead
Pin 43 (HEGO L) - dead
Pin 44
Pin 45 (Barometric Pressure) - dead
Pin 46 (SIG RTN) - dead
Pin 47 (TP) - dead
Pin 48 (STI) - dead
Pin 49 (HEGO GND) -
Pin 50 (MAF) - dead
Pin 51
Pin 52 (INJ 8) - dead
Pin 53
Pin 54 (WAC) - dead
Pin 55
Pin 56 (PIP) - power
Pin 57 (VPWR) - dead
Pin 58 (INJ 1) - dead
Pin 59 (INJ 2) - dead
Pin 60 (PWR GND) - good

Where there are blanks there is nothing going to that pin.
The fuel injector pins are dead because those wires are signal wires going to the injectors. The red wire at each of the injectors had power with the EEC plugged in. There's no power at the red wire now with the EEC disconnected. Most of the other pins that are dead are dead because they too are return or signal wires to or for the EEC.
If someone could go over this and give a response it'd be greatly appreciated. Thanks again for reading!
 
Last edited:

Purdytang9

Active User
Apr 12, 2017
54
5
18
31
#9
I bought one of those high torque starters also and i had to run another wire from the starter to the starter solenoid on the fender...i chased a cats tail on that one myself
 
Sep 19, 2016
19
5
13
Chicago, IL
#10
I bought one of those high torque starters also and i had to run another wire from the starter to the starter solenoid on the fender...i chased a cats tail on that one myself
When I installed my high torque starter I was going to do just that, then I realized that doing just that is not necessary. I created a jumper wire between the large stud and the smaller stud. Use at least 10 gauge wire.
 

jrichker

StangNet's favorite TOOL
SN Certified Technician
Mar 10, 2000
25,866
2,131
224
72
Dublin GA
#12
Pin 1 is the keep alive voltage for the computer's memory. You definitely need to fix that.

Computer will not go into diagnostic mode on 86-90 models 5.0 Mustangs

Disconnect the battery positive terminal before making any resistance checks.
The voltage drop in the ground cable will cause incorrect resistance readings.


How it is supposed to work:
The black/white wire (pin 46) is signal ground for the computer. It provides a dedicated ground for the EGR, Baro, ACT, ECT, & TPS sensors as well as the ground to put the computer into self test mode. If this ground is bad, none of the sensors mentioned will work properly. That will severely affect the car's performance. You will have hard starting, low power and drivability problems. Since it is a dedicated ground, it passes through the computer on its way to the computer main power ground that terminates at the battery pigtail ground. It should read less than 1.5 ohms when measured from anyplace on the engine harness with the battery pigtail ground as the other reference point for the ohmmeter probe.

What sometimes happens is that the test connector black/white wire gets jumpered to power which either burns up the wiring or burns the trace off the pc board inside the computer. That trace connects pins 46 to pins 40 & 60.

The STI (Self Test Input) is jumpered to ground to put the computer into test mode. Jumpering it to power can produce unknown results, including damage to the computer. The ohm test simply verifies that there are no breaks in the wiring between the test connector and the computer input.

How to test the wiring:
With the power off, measure the resistance between the computer test ground (black/white wire) on the self test connector and battery ground. You should see less than 1.5 ohms.

attachment.php?attachmentid=58312&stc=1&d=1242744354.gif


If that check fails, remove the passenger side kick panel and disconnect the computer connector. There is a 10 MM bolt that holds it in place. Measure the resistance between the black/white wire and pin 46 on the computer wiring connector: it should be less than 1.5 ohms. More than 1.5 ohms is a wiring problem. If it reads 1.5 ohms or less, then the computer is suspect. On the computer, measure the resistance between pin 46 and pins 40 & 60: it should be less than 1.5 ohms. More than that and the computer’s internal ground has failed, and the computer needs to be repaired or replaced.

See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix for the computer internal signal ground.

If the first ground check was good, there are other wires to check. Measure the resistance between the STI computer self test connector (red/white wire) and pin 48 on the computer main connector: it should be less than 1.5 ohms. More than 1.5 ohms is a wiring problem

The following is a view from the computer side of the computer wiring connector: it is for an A9L, A9P computer.
eec-iv-computer-connector-for-5-0-mustang-gif.88243.gif


a9x-series-computer-connector-wire-side-view-gif.71316.gif


Diagram courtesy of Tmoss & Stang&2birds

Check out the diagram and notice all the places the black/white wire goes. Almost every sensor on the engine except the MAF is connected to it.

88-91_5.0_EEC_Wiring_Diagram.gif


See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine

See the graphic for the 10 pin connector circuit layout.
?temp_hash=3ef2497fff29a7a9daee955cf93e5805.jpg




Code 14 - Ignition pickup (PIP) was erratic – the Hall Effect sensor in the distributor is failing. Bad sensor, bad wiring, dirty contacts. Factory tach will sometimes read erratically.

Revised 8-Apr-2017 to correct SPOUT problem symptoms wording

The PIP is a Hall Effect magnetic sensor that triggers the TFI and injectors. There is a shutter wheel alternately covers and uncovers a fixed magnet as it rotates. The change in the magnetic field triggers the sensor. They are often heat sensitive, increasing the failure rate as the temperature increases.

PIP Sensor functionality, testing and replacement:
The PIP is a Hall Effect magnetic sensor that triggers the TFI and injectors. There is a shutter wheel alternately covers and uncovers a fixed magnet as it rotates. The change in the magnetic field triggers the sensor. A failing PIP sensor will often set code 14 in the computer. They are often heat sensitive, increasing the failure rate as the temperature increases.

Some simple checks to do before replacing the PIP sensor or distributor:
You will need a Multimeter or DVM with good batteries: test or replace them before you get started.. You may also need some extra 16-18 gauge wire to extend the length of the meter’s test leads.
Visual check first: look for chaffed or damaged wiring and loose connector pins in the TFI harness connector.
Check the IDM wiring – dark green/yellow wire from the TFI module to pin 4 on the computer. There is a 22K Ohm resistor in the wiring between the TFI and the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 22,000 ohms +/- 10%.
Check the PIP wiring - dark blue from the TFI module to pin 56 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
Check the SPOUT wiring – yellow/lt green from the TFI module to pin 36 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
Check the black/orange wire from the TFI module to pin 16 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
Check the red/green wire; it should have a steady 12-13 volts with the ignition switch on and the engine not running.
Check the red/blue wire; it should have a steady 12-13 volts with the ignition switch in Start and the engine not running. Watch out for the fan blades when you do this test, since the engine will be cranking.
If you do not find any chaffed or broken wires, high resistance connections or loose pins in the wiring harness, replace the PIP sensor or the distributor.

The PIP sensor is mounted in the bottom of the distributor under the shutter wheel. In stock Ford distributors, you have to press the gear off the distributor shaft to get access to it to replace it. Most guys just end up replacing the distributor with a reman unit for about $75 exchange

PIP problems & diagnostic info
The PIP signal level needs to be above 6.5 volts to trigger the computer to pulse the fuel injectors, but only needs to be 5.75 volts to trigger the TFI module. Hence with a weak PIP signal, and the SPOUT in, you could get spark but no injector pulse. You will need an oscilloscope or graphing DVM to measure the output voltage since it is not a straight DC voltage.

See http://www.wellsmfgcorp.com/pdf/counterp_v8_i2_2004.pdf and http://www.wellsmfgcorp.com/pdf/counterp_v8_i3_2004.pdf for verification of this little detail from Wells, a manufacturer of TFI modules and ignition system products.


The following are diagrams courtesy of Tmoss & Stang&2birds

Complete computer, actuator & sensor wiring diagram for 88-90 Mass Air Mustangs


TFI module differences & pin out




See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring; http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.



TFI module wiring for 94-95 Mustang GT
http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-IgnitionControlModule.gif

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 88-90 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

O2 sensor wiring harness
http://www.veryuseful.com/mustang/tech/engine/images/mustangO2Harness.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pin out
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

Mustang 5.0 Lights and Radio schematic, by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxLights-Radio_diag.gif

87-92 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang87-92 PowerWindowWiring.gif

93 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang93PowerWindows.gif

T5 Cutaway showing T5 internal parts
http://www.veryuseful.com/mustang/tech/engine/images/5_Speed_Cutaway_Illustrated.jpg

Visual comparison of the Ford Fuel Injectors, picture by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/Ford_Injector_Guide.jpg

Convertible top motor wiring http://www.veryuseful.com/mustang/tech/engine/images/mustang88VertTopMotorCkt.gif

Engine mounted fuel injector harness
http://www.veryuseful.com/mustang/tech/engine/images/mustangEngineHarness.gif

Location of the TPS, IAB, and the 10-pin connectors on a 5.0, picture by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/TPS_IAB_Pic.jpg

Starter circuit
http://forums.stangnet.com/attachment.php?attachmentid=21328&d=1080916057

Alternator diagram for 94-95 Mustangs.
http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-Alt.gif
 
Sep 19, 2016
19
5
13
Chicago, IL
#13
Pin 1 is the keep alive voltage for the computer's memory. You definitely need to fix that.

Computer will not go into diagnostic mode on 86-90 models 5.0 Mustangs

Disconnect the battery positive terminal before making any resistance checks.
The voltage drop in the ground cable will cause incorrect resistance readings.


How it is supposed to work:
The black/white wire (pin 46) is signal ground for the computer. It provides a dedicated ground for the EGR, Baro, ACT, ECT, & TPS sensors as well as the ground to put the computer into self test mode. If this ground is bad, none of the sensors mentioned will work properly. That will severely affect the car's performance. You will have hard starting, low power and drivability problems. Since it is a dedicated ground, it passes through the computer on its way to the computer main power ground that terminates at the battery pigtail ground. It should read less than 1.5 ohms when measured from anyplace on the engine harness with the battery pigtail ground as the other reference point for the ohmmeter probe.

What sometimes happens is that the test connector black/white wire gets jumpered to power which either burns up the wiring or burns the trace off the pc board inside the computer. That trace connects pins 46 to pins 40 & 60.

The STI (Self Test Input) is jumpered to ground to put the computer into test mode. Jumpering it to power can produce unknown results, including damage to the computer. The ohm test simply verifies that there are no breaks in the wiring between the test connector and the computer input.

How to test the wiring:
With the power off, measure the resistance between the computer test ground (black/white wire) on the self test connector and battery ground. You should see less than 1.5 ohms.

View attachment 581849

If that check fails, remove the passenger side kick panel and disconnect the computer connector. There is a 10 MM bolt that holds it in place. Measure the resistance between the black/white wire and pin 46 on the computer wiring connector: it should be less than 1.5 ohms. More than 1.5 ohms is a wiring problem. If it reads 1.5 ohms or less, then the computer is suspect. On the computer, measure the resistance between pin 46 and pins 40 & 60: it should be less than 1.5 ohms. More than that and the computer’s internal ground has failed, and the computer needs to be repaired or replaced.

See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix for the computer internal signal ground.

If the first ground check was good, there are other wires to check. Measure the resistance between the STI computer self test connector (red/white wire) and pin 48 on the computer main connector: it should be less than 1.5 ohms. More than 1.5 ohms is a wiring problem

The following is a view from the computer side of the computer wiring connector: it is for an A9L, A9P computer.
View attachment 581850

View attachment 581851

Diagram courtesy of Tmoss & Stang&2birds

Check out the diagram and notice all the places the black/white wire goes. Almost every sensor on the engine except the MAF is connected to it.

View attachment 581852

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine

See the graphic for the 10 pin connector circuit layout.
View attachment 581853



Code 14 - Ignition pickup (PIP) was erratic – the Hall Effect sensor in the distributor is failing. Bad sensor, bad wiring, dirty contacts. Factory tach will sometimes read erratically.

Revised 8-Apr-2017 to correct SPOUT problem symptoms wording

The PIP is a Hall Effect magnetic sensor that triggers the TFI and injectors. There is a shutter wheel alternately covers and uncovers a fixed magnet as it rotates. The change in the magnetic field triggers the sensor. They are often heat sensitive, increasing the failure rate as the temperature increases.

PIP Sensor functionality, testing and replacement:
The PIP is a Hall Effect magnetic sensor that triggers the TFI and injectors. There is a shutter wheel alternately covers and uncovers a fixed magnet as it rotates. The change in the magnetic field triggers the sensor. A failing PIP sensor will often set code 14 in the computer. They are often heat sensitive, increasing the failure rate as the temperature increases.

Some simple checks to do before replacing the PIP sensor or distributor:
You will need a Multimeter or DVM with good batteries: test or replace them before you get started.. You may also need some extra 16-18 gauge wire to extend the length of the meter’s test leads.
Visual check first: look for chaffed or damaged wiring and loose connector pins in the TFI harness connector.
Check the IDM wiring – dark green/yellow wire from the TFI module to pin 4 on the computer. There is a 22K Ohm resistor in the wiring between the TFI and the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 22,000 ohms +/- 10%.
Check the PIP wiring - dark blue from the TFI module to pin 56 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
Check the SPOUT wiring – yellow/lt green from the TFI module to pin 36 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
Check the black/orange wire from the TFI module to pin 16 on the computer. Use an ohmmeter to measure the wire resistance from the TFI to the computer. You should see 0.2-1.5 ohms.
Check the red/green wire; it should have a steady 12-13 volts with the ignition switch on and the engine not running.
Check the red/blue wire; it should have a steady 12-13 volts with the ignition switch in Start and the engine not running. Watch out for the fan blades when you do this test, since the engine will be cranking.
If you do not find any chaffed or broken wires, high resistance connections or loose pins in the wiring harness, replace the PIP sensor or the distributor.

The PIP sensor is mounted in the bottom of the distributor under the shutter wheel. In stock Ford distributors, you have to press the gear off the distributor shaft to get access to it to replace it. Most guys just end up replacing the distributor with a reman unit for about $75 exchange

PIP problems & diagnostic info
The PIP signal level needs to be above 6.5 volts to trigger the computer to pulse the fuel injectors, but only needs to be 5.75 volts to trigger the TFI module. Hence with a weak PIP signal, and the SPOUT in, you could get spark but no injector pulse. You will need an oscilloscope or graphing DVM to measure the output voltage since it is not a straight DC voltage.

See http://www.wellsmfgcorp.com/pdf/counterp_v8_i2_2004.pdf and http://www.wellsmfgcorp.com/pdf/counterp_v8_i3_2004.pdf for verification of this little detail from Wells, a manufacturer of TFI modules and ignition system products.


The following are diagrams courtesy of Tmoss & Stang&2birds

Complete computer, actuator & sensor wiring diagram for 88-90 Mass Air Mustangs
88-91_5.0_EEC_Wiring_Diagram.gif


TFI module differences & pin out
TFI_5.0_comparison.gif




See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring; http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.



TFI module wiring for 94-95 Mustang GT
http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-IgnitionControlModule.gif

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 88-90 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

O2 sensor wiring harness
http://www.veryuseful.com/mustang/tech/engine/images/mustangO2Harness.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pin out
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

Mustang 5.0 Lights and Radio schematic, by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxLights-Radio_diag.gif

87-92 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang87-92 PowerWindowWiring.gif

93 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang93PowerWindows.gif

T5 Cutaway showing T5 internal parts
http://www.veryuseful.com/mustang/tech/engine/images/5_Speed_Cutaway_Illustrated.jpg

Visual comparison of the Ford Fuel Injectors, picture by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/Ford_Injector_Guide.jpg

Convertible top motor wiring http://www.veryuseful.com/mustang/tech/engine/images/mustang88VertTopMotorCkt.gif

Engine mounted fuel injector harness
http://www.veryuseful.com/mustang/tech/engine/images/mustangEngineHarness.gif

Location of the TPS, IAB, and the 10-pin connectors on a 5.0, picture by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/TPS_IAB_Pic.jpg

Starter circuit
http://forums.stangnet.com/attachment.php?attachmentid=21328&d=1080916057

Alternator diagram for 94-95 Mustangs.
http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-Alt.gif
Thank you very much! I'll make a list of what to check and post my results.
 
Sep 19, 2016
19
5
13
Chicago, IL
#14
Reporting back!

I made a list of what to check and here's what I've found.

Pin 1 - dead with key OFF, but has power with key in RUN (KOEO). I'm going to test this again today to verify this.
I don't feel this is right, anyone have some input on this? I'd appreciate if someone could test this on their own car.

Resistance between computer test ground (black/white wire) and battery ground
- My ohmmeter read nothing.

Resistance between computer test ground (black/white wire) and pin 46 @ EEC connector
- 1.4 ohms

ON COMPUTER - resistance between pin 46 and pins 40 & 60
- 1.1 ohms between 46 and 40
- 1.1 ohms between 46 and 60

Resistance between STI self test connector and pin 48 @ EEC connector
- 1.3 ohms

Resistance between IDM wire @ TFI module and pin 4 @ EEC connector
- 21.9k ohms

Resistance between PIP wire @ TFI module and pin 56 @ EEC connector
- 1.4 ohms

Resistance between SPOUT wire @ TFI module and pin 36 @ EEC connector
- 1.4 ohms

Resistance between black/orange wire @ TFI module and pin 16 @ EEC connector
- 1.4 ohms

Red/green wire @ TFI module with key in RUN
- battery power

Red/blue wire @ TFI module while cranking car over
- 8.1 volts with the battery at approximately 11.5 volts. I measured what the battery was at while cranking as well, this read out to be 9.9 volts.

Car still isn't starting. Is this my computer? I'm going to test to see if my EEC relay is getting power from the black/orange wire that goes to pin 1. I have power going through this wire past it's fusible link, so it is not blown. I'm also going to see if it has power at the FP relay with the key in run.
 
Last edited:

jrichker

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#15
Pin 1 - dead with key OFF, but has power with key in RUN (KOEO). I'm going to test this again today to verify this.
I don't feel this is right, anyone have some input on this? I'd appreciate if someone could test this on their own car.
Go back and look at the diagram =Pin 1 on the computer connects directly connects to the battery through the fuse link on the battery side of the starter solenoid.

 
Sep 19, 2016
19
5
13
Chicago, IL
#16
I have verified that pin 1 has power while in run.

I'm more than sure that the EEC relay is fine, as all of my injectors and everything else that is powered by the red wire from pins 37 and 57 have power while the key is in run.

I fixed a torn wire by my starter solenoid today. There is a brown wire that comes out of the bunch of wires with fusible links that was cut. I spliced it back into the set.

While I was in the area, I checked my computer ground (push on connector that leads to ground from battery negative). This is good.

I have spark now! The car is still not starting. I'm very sure that my computer is bad with this said.
 
Sep 19, 2016
19
5
13
Chicago, IL
#17
Go back and look at the diagram =Pin 1 on the computer connects directly connects to the battery through the fuse link on the battery side of the starter solenoid.

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I'll check this again. I've looked at this diagram and a few more to verify that yes, the computer should always have power at pin 1. Thank you for the information and diagrams.
 

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