EEC-4 Codes Not Listed From ECA, MIL and Fuel Pump Stays On With KOEO

Hello All;
Here's the summary first because this is a long post:
Is there a newer Pinpoint Test QA 'No Codes/Codes Not Listed' for the 89 EEC-4 processor? My Motor Manual is from 1991 and covers 89 and 90.
Specificly QA5 which is the test for Self Test Output Short to Ground is the one I'm questioning as to accuracy.
QA5 says measure the resistance of the Self Test Output at the Output Test Connector to the engine ground. QA5 says it should be more than 10,000 ohms but it doesn't make sense to me because this is the MIL light circuit and the MIL light circuit is shared through the feed (common) side of the MIL Light with all the guages and other lights in the instrument cluster. QA5 says if the resistance is under 10,000 ohms, (I have 35 ohms with the MIL light installed and an open circuit with the MIL light removed), then the problem is a short to ground in the MIL circuit.
I'm not saying this is wrong, I'm just concerned that the book might be wrong because it is 15 years old and that may cause me to waste time tracing down a 35 ohm short that might not be the problem at all.
Ignoring this and going to QA9 because the MIL is staying on with the KOEO including while cranking, it tells me to go to ML1. This test says the same thing as QA5 except it says check the resistance at the other end of the STO at pin 17 at the breakout box to ground pin 40. Again it says if there is a short to fix the MIL circuit.
Could the processor be causing this short to ground of 35 ohms with the MIL light installed? This has me scratching my head because when I remove the MIL bulb the STO circuit between the processor pin 17 and MIL light is fine. The cluster looks fine, no burns and all the guages work. This leads me to believe the test in my book may be wrong for the 88-89 with the MIL as opposed to the 87 and lower which didn't have the MIL. This wouldn't be the first time I've run across this.
Also would no Self Test Output (No Codes) from the ECA and a 29,000 ohm resistance at the Fuel Pump Relay harness negative circuit to ground, the one that goes to the timer in the ECA that grounds the relay turning on the pump for 2 seconds with the KOEO be a sign of a bad processor? This 29K resistance goes away when I unplug the processor. This resistance is causing the fuel pump to stay on with the KOEO. It seems to be just enough to charge the relay turning on the pump.
My heart tells me the processor is bad because the fuel pump is staying on and I cant get any codes but I want to make sure my book is telling me the right thing before I plug up a new processor and wanted to run this across everyone here as well.
Here are the fine points and thanks::
It's an 89 Ranger with a 2.3 EFI and 8 plug DIS ignition that is blowing black smoke and backfiring through the intake during WOT. It happened right away like throwing a switch. The check engine (MIL) light is staying on all the time including during cranking like the processor is in 'Falure Mode Effects Management' or FMEM but without the accompanying code 98 which is normally outputed when FMEM is in effect.
I tried to run a KOEO self test and no codes were outputed (no code 11, nothing) along with no actuator/solenoid movement. I used an analog voltmeter and it stayed at 12 volts, (no needle sweep). The STO circuit isn't working.
I opened up my 1989-1990 edition Motor' Truck Engine Tune-Up and Electronics Manual and after doing the usual checking of those pesky grounds and connectors, sensor and output values, went to 'Pinpoint Test QA No Codes/Codes not Listed' after being refered there from Quick Test 3.0. I did the following:
QA1 Check For Voltage Ref. (Good at 5.0 volts)
QA2 Check Self Test Input (STI) Continuity (Good)
QA3 Check Self Test Output (STO) Continuity (Good)
QA4 Check HEGO Sensor Ground Continuity (This showed 1/2 ohm between Breakout Box pin 49 and pin 40/60 at the box and I believe this would be the same as going from the HEGO Ground to 'test pin 49 HEGO Input' because 40/60 1is grounded to the motor as well.) This should be fine. on to the next step.
QA5 Here is where the problem came into the picture as refered to in the above summary. With the KOEO the STO circuit pin 17 at the ECA and the MIL is fine with the MIL bulb removed but when I replace the bulb the resistance goes to 35 ohms. i dont know if the instrument cluster, processor, or book is at fault. With this in mind I continued on.
QA6 I skipped this because it is for the 'Intermittent NDS' requiring a Engine Running Self Test and if no codes are outputed it tells you to go right back to Pinpoint Test QA. On to the next.
QA7 Check Power Relay for Always On This test worked out fine. The power relay cuts on and off with the key.
QA8 N/A
QA9 This ask the question 'is the MIL light aways on? Yes. This concluded Pinpoint Test QA and sent me to ML1 which told me the same thing as QA5, fix the short in the MIL circuit.
If the book is OK then where would a 35 ohm short be?
Thanks again, scratching head,
Ed
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You said it yourself... the STO and MIL share the cicuit, didnt you?
And you said STO is 10k or more with bulb out.. thus it isnt shorted to ground. Which you verify by saying it's 12 volts... if the STO/MIL was shorted to ground, the light wouldnt come on.
Put the leads of the meter on the bulb.. yep, 35 ohms
And I dont think the current allowed by a 29k resistance is enough to energize that FP relay.. but I could be wrong. You need to read the VOLTAGE at the relay feed test point to determine the proper operation
So either you are reading the scales wrong or you have a real weird thing going on there.
Bottom line: Unless you have a weird grounding problem in the harness at the PCM connector, the PCM is probably fried.
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The bulb in this case was 6 ohms across it so that left 29 ohms unaccounted for between the common feed on the other side of the MIL bulb toward the ignition switch. which didn't go away BTW when I disconnected the ignition switch which feeds the whole thing, hence the question with the book being right or not concerning theQA pinpoint test. This is my main concern, written accuracy in the 16 year old Motor manual.
The 29K resistance at the FP relay at the negative inducting coil wire going to the processors' timer is causing the FP relay to energize. At first I thought it was because of a leaking diode but it's coming straight from the FP timer circuit in the processor because there is no diode to bleed current that I know of..
Those processors are pricey. I'd hate to plug one in to watch it blow because of a bad wire.
Fried processor, yes I feel you're right because of the FP if nothing else. I'm wondering if a strange wiring short caused the old one to blow, specificly that 29 ohms I can't account for, or if 300,000 miles, and 16 years of wear and tear on the old processor in Houstons' 100 degree summer heat finally took it's toll on the old part.
Like you say the processor is most likely shot. This one has me really thinking though. I've never seen a problem like this where the fuel pump runs and the STO wont put out. It just smells of a short somewhere and I'm worried I may blow a new processor.
Fords are great and last forever until they break down. :-)
Ed

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here's a dumb question... have you tried it without the MIL bulb installed?

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installed?
Without the bulb the short goes away yes because between the instrument cluster MIL wire and processor pin 17 STO there is no short. The motor still runs bad.. That's why I'm wondering about this part of the QA pinpoint test as wrote:
"QA5 STO Short To Ground" "(1) Key off." "(2) Breakout box installed processor disconnected. DVOM on 200,000 ohm scale." "(3) Measure resistance between STO at self test connector and engine block ground." "(4) Is resistance less than 10,000 ohms?"
The resistance is less at 35 ohms. The location of the resistance is between the MIL bulb feed and the engine ground. It's going to the STO through the instrument cluster as the MIL feed feeds everything else including the guages on the cluster.
The answers for the test are:
"(A) Yes resistance is less than 10,000 ohms: Remove breakout box. Reconnect processor. Service STO or MIL/SIL circuit for short to ground. Rerun quick test."
"(B) No: Go to QA6"
Did the person writing that part of the book just consider the MIL/STO circuit starting at the MIL bulb and just write it wrong or is there a 35 ohm short in my instrument cluster between the MIL feed and ground that blew the old processor?
--------------------------------------------------------
The 29K at the FP relay is there with or without the bulb so that tells me the processor is bad.
I just dont want to blow a new one. Those suckers take days to get. :-)
Ed
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Come on... quit over-informing!
Does the car have the bad driveability symptoms with the bulb removed, yes or no??????!
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Sorry for over informing :-)
No it didn't change. See the other reply, bad ECA. Thanks again.

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Look, Glen.... for one thing you are placing far too much emphasis on resistance reading and it's confusing. I know electronics and I used to design logic and driver circuits.
In relay and lamp drivers, 29K is usually inconsequential...unless the relay is of the 'current-sense' type which it isnt. Those are used as sensors not switchers.
What you need to do FIRST is actually determine FOR SURE that the opposite side of that MIL lamp circuit is supposed to be attached to the cluster ground. The NORMAL design is to ground circuits to activate them. I dont have the diagrams available to verify which way Ford does it on the CEL/MIL.
Second... if it's true that the non-switched (cluster) side is grounded, and the light is on at normal intensity, there is NO short in that lead to the lamp! Forget the lead resistance.
The problem THEN would be that the driver itself, inside the PCM, is always turned on... or shorted Meaning the PCM is dead.
There is no external input I can think of that would cause the PCM to simply toast itself, other than a 12v supply over-voltage surge such as MIGHT occur if your Alt. Voltage Regulator went temporarilly belly up and your battery couldnt absorb the current (thus keeping voltage down) for some reason
I'm sorry.. I dont usually advocate this but now is the time to throw a used part at the problem.
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Agreed.
I'm getting an ECA on Tuesday with a lifetime warranty for 109.00. I took the old one apart and a can type capacitor had melted down and actually burned spilling it's guts everywhere.

always
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Virtually all the EEC4 PCM outputs of that vintage are 'low-side' drivers. The MIL is connected to +12V (through the ignition switch) on the constant supply side. The PCM provides the ground to turn it on. If the MIL lamp is out, a test light may be connected to STO instead, with its other lead returned to +12V (not ground). Older manuals talk about connecting an analog voltmeter in the same fashion. Those pull a bit of current (a fraction of 1 mA, typically). If you want to use a digital multimeter and the MIL lamp is removed, provide a load to +12V (something like a 10K resistor will do). Not sure, but I believe that with the ignition off, STO is still driven to ground, because of the constant (unswitched) power available to the PCM. So measuring resistance in that state will not provide any useful information -- it will appear to be shorted to ground. Essentially, the way to tell is to put the PCM in a diagnostic mode (invoke the KOEO test by grounding STI). STO should then embark on its sequence of flashes. If it remains constantly driven to ground, there is something obviously wrong with the PCM.

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Don't read too much into the resistance value on these sorts of tests. I'm not particularly familiar with the PPTs you are performing but asking if resistance is above 10,000 ohms on a circuit is Fords way of asking if there is continuity. Similarly, when they are asking if resistance is 5 ohms or less, they are also checking continuity. Additionally, these manuals can and do contain misprints.... they also can contain inappropriate procedures for the test we are performing.
It becomes important for us to study the test step and determine just what it is the engineers wanted us to test... in the case of QA5, they want to see no continuity between the STO connection and engine ground.....
OK... I got off my fat duff and scanned briefly through the PC/ED for 92 (sorry, the oldest manual I have on hand but should be pertinent). Couldn't check the EVTM since my laptop is at home with a weak battery and my power cord is at work...... In a case like yours, it is excrutiatingly important to work through the quick tests in the correct order... neglecting steps or performing inappropriate tests WILL have us replace a module, perhaps needlessly.
Looking at QT3, we see towards the end, that it makes a difference if we pull a pass code or if we pull no codes at all during the KOEO self test. Remeber that, during KOEO, On Demand codes are displayed first (this is where we should see our first PASS (11 or 111) code.... this is followed by a separator code which is followed by a Conitnuous Memory code. If you ARE seeing 11-10-<any code other than a pass> or 111-10-<any code other than pass>, you would need to verify that the <anycode other than pass> is not part of your concern. If you retrieve 11-10-11 or 111-10-111, you would go to symptom charts and would be directed to ML1. If you retrieve no codes at all... this includes PASS codes, you would go to QA.
It is important that we do NOT perform any tests that we aren't specifically directed to. If the PC/ED directed you to go to ML1, you should ne be in QA unless a test step has you go there... vice-versa
HTH
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Jim and Backyard Mechanic first off I want to thank you both.
The two of you seem to be saying the 35 ohm resistance at the MIL bulb is no big deal because it's over 5 ohms (not shorted to ground) and when I unplug the bulb the short goes away.
Because the timer in the processor is shorted causing the fuel pump to run all the time with the key on and because no codes are outputed and the light is staying on all the time including during cranking which would mean the processor is running in hardware mode only ignoring software altogether, i think I'll take a leap of faith and install a new processor.
Now all I have to do is find one. I may buy the Cardone 78-4351. Takes a few days but has a lifetime warranty.
Hopefully when I plug it in it will hold. All the other voltages and resistances at the breakout box are showing to be fine.
Looks like I'll just bite the bullet and hope for the best.
I'll let everyone know what happens.
Ed

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I had an 85 T-Bird ,3.8 with EEC-V The fuel pump power relay went bad resulting in the pump turning itself on every 15 or 20 seconds even with the key off and out of the ignition until the battery ran down over night.
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Oh I know what that's like. I had a few of those myself.
I also had an old 70 something Ford truck I left in gear with the break off and one morning I went to open up the shop to find it in front of the support beam holding up the garage with a burnt up starter, a busted headlight, and a dead battery. Seems the starter solenoid kicked in all by itself. Ever since then I disconnect the battery before working under the hood on a Ford especially.
Ed

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