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Discussion Starter · #1 · (Edited)
So ive been working on my taurus for a week now and ive been all over this forum scouring every slightly related post i could find and finally decided to make an account to ask my question.
My car is a 3.0l '06 Taurus with vulcan motor. Up until last week it has always ran fine and gets driven every day. One day i started her up, drove down the street about 100 feet and it just stalled out on me with no warning or sputtering or anything. I was able to get it started back up and drove it the 100ft back to my driveway and parked it, it was running very odd with no power. (car has never overheated or anything like that, all fluids are good). I was about to change the waterpump anyway cuz it was starting to leak on me so i changed the waterpump and started diagnosing this new problem.

The only code it throws is P0352, which is Ignition B Coil Circuit and the #2 Cylinder. I do some reading and find out that when the PCM doesnt get a pulseback - it shuts off the injector to that cylinder, OK so that makes sense. Its running on 5 cylinders. I pull the plugs off the coil pack (this one has the singular ignition coil pack that all wires go to) and all of the connections on the coil pack itself are good EXCEPT the connector for #2 - it is all white/burnt/corroded and also the pack has several cracks, i also find that the ignition wire for the #2 cylinder has a bad connection where it plugs into spark plug.. So i think i find my issue - bad connection on coil pack AND wire connection for #2 cylinder. So I replace coil pack - all 6 plugs and wires (all Motorcraft).

I clear the codes, i try draining the PCM capacitors, and the code STILL keeps coming on and shutting off my #2 cylinder. Sometimes it feels like its firing perfectly for the first half mile of driving (only after clearing codes/PCM) but then it starts losing power and the exhaust starts getting louder and i can tell its running on 5 cylinders again. But other than that, it is consistent from the time i start my car, it doesnt come and go. And it just seems to get progressively worse the warmer the car gets. Im not sure what to do im losing my mind and almost out of money for new parts. I tried pulling the PCM off and spraying some electrical cleaner in there and making sure the pins werent bent. I have looked all over for any broken wires or bad grounds and i dont see anything obvious. i dont see how it could be the PCM because i think the coil driver runs 2 cylinders off each driver, not just 1.

i need help please.

EDIT: just for some extra info , i should probably mention that when i check with the OBD reader im also getting a "OL Fault" and the FIRST set of fuel trims are all at 0. The ones im referring to say STFT B1% and STFT B2% i think. Because there was also a set of 4 fuel trims at the bottom of the scanner that all had a reading on them but the first set is at 0. Where i also watched a video on youtube of another guy with the same OL fault and trim readings the same as mine and his was a PCM issue. How would i know if its PCM?
 

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The code for the ignition coil is the primary side and not the secondary side. So you have to check the coil, which you said you replaced. The other is the actual wiring from the PCM to the coil. You should find the pin on the PCM connector and ohm it out to the connector to the coil. If that checks out then maybe the PCM output drivers could be bad. I had a similar issue on my 06 but it was that the coil primary was bad.
Until you eliminate the primary coil code the others about fuel trims will read bad because of the unburnt fuel from #2.
 

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Discussion Starter · #3 · (Edited)
The code for the ignition coil is the primary side and not the secondary side. So you have to check the coil, which you said you replaced. The other is the actual wiring from the PCM to the coil. You should find the pin on the PCM connector and ohm it out to the connector to the coil. If that checks out then maybe the PCM output drivers could be bad. I had a similar issue on my 06 but it was that the coil primary was bad.
Until you eliminate the primary coil code the others about fuel trims will read bad because of the unburnt fuel from #2.
When i google this code, it tells me that it could be the primary OR secondary circuit with this code. What makes you say it could only be the primary? And the issue im having with ohming the wire from the PCM to the singular coil pack is that there are only 4 wires that go to the coil pack. One constant 12v, and 3 leads which control 2 cylinders each. So i only have one wire going from PCM to cylinders 2+6 that controls the spark for both. So i dont even understand how one cylinder could not be firing because i dont have any problems with the other cylinder on that same wire. Which makes me think its the spark plug or spark plug wire but ive replaced both of those as well. Its really throwing me for a loop. And also im having trouble finding any reliable info on this specific ignition system because all the other taurus seem to have the COPs with six different coil packs. This one only has one singular coil pack that runs all 6 cylinders.

how exactly would i go about ohming the wires for cylinder 2? i found the diagram for the PCM. One terminal labeled ignition Coil B with one wire going to coil pack, but that one wire controls 2 different cylinders? So if the wire was bad wouldnt it affect both? Or is there a different way to test how it grounds each individual cylinder?

edit: actually i can test from where the spark plugs connect to the coil pack, cant I? so i can just test from pcm Ignition B terminal to either coils where the spark plugs connect.
 

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The ignition system is called a waste firing system and it fires the plug in both cylinders at the same time where one is on the exhaust stroke and the main firing is the one with a fuel charge at TDC. Not sure if it is a cheap way to design a system or a way to reduce any unburned fuel in the cylinder.I believe it is only for the primary side because the secondary side cant be measured to set a code other than a misfire code and there is a specific code for each cylinder misfire.

You can ohm out the coil but in my case it ohmed out just like a new coil but it was under heat and load that the primary broke down.

I had the exact same code on my 06 and it was the coil pack. It started as a hesitation on the torque converter lockup at 40-45 mph but finally set the code going up a long hill and lost power.
 

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Discussion Starter · #6 ·
Does it really throw the same P0352 code after changing the coil pack and checking the PCM connector?
Yes it started with a random stall one day and then its ran like **** ever since, throwing the code every single time. And its as soon as you start it. Doesnt ever go away. Like i said i changed the coil pack and all plugs and wires. Yesterday i went out there and swapped the plug with a different cylinder and it still throws the same P0352 code. I even ohmed the plugs and wires and they seem to be fine. And also when i pulled the cylinder 2 plug out that the code is on - it looked like the plug had at least tried to fire a few times.

As far as the PCM, like i said i dont understand how im supposed to test a connection that has one wire. There is one wire coming from PCM labeled Ignition Coil B, this same wire fires cylinders 2 & 5, and i dont have any problems with cylinder 5. But either way, i dont know how i would test to differentiate between cyl 2 and cyl 5. One prong on the PCM terminal and the other on coil pack connector but the same terminal controls both cyl. So i dont understand. The wire coming from PCM has to be good or else cyl 5 would have issues also, right?
 

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Coil B powers cylinders 2 and 6 (agreed, it is somewhat counter-intuitive). Given the P0352, I guess the engine runs on 4 cylinders when this happens. You should be able to take out the spark plug wires of either 2 or 6 or both from the coil pack (they are of course across from each other) and basically nothing happens. Any of the other 4 wires and the engine dies.
 

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Discussion Starter · #8 ·
Coil B powers cylinders 2 and 6 (agreed, it is somewhat counter-intuitive). Given the P0352, I guess the engine runs on 4 cylinders when this happens. You should be able to take out the spark plug wires of either 2 or 6 or both from the coil pack (they are of course across from each other) and basically nothing happens. Any of the other 4 wires and the engine dies.
I wanted to try that test but I heard it would damage the ignition wires if there was spark going thru it so I didnt try. I just tried backprobing the coil pack electrical connector with a paperclip and used a test light on all 4 wires. The 3 leads to coils and constant 12v. If I turn the key on but dont start the car- I'm getting 12v constant from all 4 wires. So that means the wires from PCM are good right?? I'm getting 12v to all 3 coils. I want to test if they each turn on and off when I start the car but I dont have anyone to turn the key for me right now.

If I can test whether they turn off and on when you start the car - then I will know if that B coil is ever grounding itself right? So if the B coil test light stays on with ignition then that means it's not grounding itself and I have a bad ground wire possibly? And its shutting the cylinder off since its staying constant 12v and not able to ground?
 

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The coil wires will be constant voltage all the way back to the PCM because I believe the PCM drivers closes the circuit internal to it so it will have voltage all the time on the wires. Have you checked back at the PCM pins on the plug. Also has your ignition coil noise suppressor been damaged or shorted out? It is the C shape plastic device on the intake stud where the sparkplug wires run by in the front.
 

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I think you're right. Looking at the electrical diagram in the Haynes manual, the coil pack looks like 3 transformers. Each of the 3 primaries is connected to 12V on one side and to the PCM other side. So I assume the PCM will pull down the wire, leading to a current in the primary and at the time of the spark, the PCM will disengage from the wire (the output FET blocks). This abruptly stops the current, leading to a current in the (probably much larger) secondary coil, leading to a spark in both spark plugs 2 and 6.

So checking the voltage on the wire to the PCM while the engine is not running should always give you 12V and doesn't prove the wire of coil B (Yellow with Red stripe according to Haynes) to the PCM is OK. I think it is best to really test the wire from the PCM to the coil pack connector.
 

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I think you're right. Looking at the electrical diagram in the Haynes manual, the coil pack looks like 3 transformers. Each of the 3 primaries is connected to 12V on one side and to the PCM other side. So I assume the PCM will pull down the wire, leading to a current in the primary and at the time of the spark, the PCM will disengage from the wire (the output FET blocks). This abruptly stops the current, leading to a current in the (probably much larger) secondary coil, leading to a spark in both spark plugs 2 and 6.

So checking the voltage on the wire to the PCM while the engine is not running should always give you 12V and doesn't prove the wire of coil B (Yellow with Red stripe according to Haynes) to the PCM is OK. I think it is best to really test the wire from the PCM to the coil pack connector.
Or just test for 12 volts at the PCM connector. Other than that it could be one of the drivers internal to the PCM or like most of the time the coil. No ground to the coil but he could check the engine ground strap to the firewall. Also recheck the location of the plug wires on the front of the coil. They are not in sequence as the in the back.
 

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Discussion Starter · #12 · (Edited)
Or just test for 12 volts at the PCM connector. Other than that it could be one of the drivers internal to the PCM or like most of the time the coil. No ground to the coil but he could check the engine ground strap to the firewall. Also recheck the location of the plug wires on the front of the coil. They are not in sequence as the in the back.
Okay so then having voltage at the coil pack connector does not necessarily mean the wire to the PCM is good, right? So I need to check for 12v constant at the Ignition B terminal on the PMC just like I did at the coil pack B terminal? Ok I'll try. I just havent done it yet because I cant get the plastic cover off the pcm becuase I dont wanna have to take the whole upper intake off and replace the gasket.

As far as the ground strap goes , that's what I've been doin for the last hour. I noticed the PCM had several grounds going there and the whole ground terminal was corroded and not grounding well so I sandpapered it down and metered to test them. Tries clearing code and driving it down the road but same thing immediately. Shuts off the cylinder. And I've double checked wire order.
'also idk about a ingition coil suppressor, ill try to find it and look at it
 

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Discussion Starter · #13 ·
I think you're right. Looking at the electrical diagram in the Haynes manual, the coil pack looks like 3 transformers. Each of the 3 primaries is connected to 12V on one side and to the PCM other side. So I assume the PCM will pull down the wire, leading to a current in the primary and at the time of the spark, the PCM will disengage from the wire (the output FET blocks). This abruptly stops the current, leading to a current in the (probably much larger) secondary coil, leading to a spark in both spark plugs 2 and 6.

So checking the voltage on the wire to the PCM while the engine is not running should always give you 12V and doesn't prove the wire of coil B (Yellow with Red stripe according to Haynes) to the PCM is OK. I think it is best to really test the wire from the PCM to the coil pack connector.
Ok ya I thought if the coil pack B primary had 12v then it was good but I guess I'll try the Pcm. I havent done it yet cuz I cant get the damn plastic shield off the PCM. I'm trying not to have to take the whole intake off and replace the gasket. I can unplug the pcm I just havent been able to get the room to pop the cover off
 

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I think the Upper Intake Manifold (UIM) gasket is not all that critical. Just put a film of oil on it and reuse it. I always take off the UIM in order to reach the spark plugs of cylinders 1, 2 and 3. Especially spark plug 1 is difficult to reach otherwise. It takes more time, but it's better for my blood pressure because I get irritated (if not angry) if I can't properly reach the part I'm working on. And that is not in line with "Zen and the Art of Motorcycle Maintenance".
 

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Discussion Starter · #15 ·
So I finally got the PCM cover off and got to testing. I have 12v constant from my primaries at the PCM plug when I turn the key on. That's including the problem B circuit. So I verified that I have 12v at the PCM and I also turned the power off and checked the resistance from PCM to coil pack connector and it tested good as well, I even tried wiggling the wires while i did it to see if there was a moving short. So pcm is getting voltage fine...

So. Damn. Does this really mean that my pcm is bad? I know I have voltage from pcm to coil now. The coil pack is brand new motor craft, its spotless and also tests out fine with meter. I unplugged the battery totally to drain the pcm capacitors and I'm about to spray it down with electronic cleaner. I just dont see how a pcm would randomly go bad and only affect this single cylinder.
 

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I think the Upper Intake Manifold (UIM) gasket is not all that critical. Just put a film of oil on it and reuse it. I always take off the UIM in order to reach the spark plugs of cylinders 1, 2 and 3. Especially spark plug 1 is difficult to reach otherwise. It takes more time, but it's better for my blood pressure because I get irritated (if not angry) if I can't properly reach the part I'm working on. And that is not in line with "Zen and the Art of Motorcycle Maintenance".
I have had/have 5 DOHC's. I have had the intake off all of them, couple more than once. Never replaced a gasket, never had any issue. Same for throttle body. I wipe off the gasket and inspect to be sure it is in place and no damage. On the matching surface, I wipe it clean and wipe a most light coating of spark plug boot grease. Lets the gasket slide a tick if needed as it goes back.
My issue is with the '05 as the TB is heated so coolant lines to deal with.
-chart-
 

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About everybody on this forum will think a faulty PCM is the unlikeliest of explanations. But we are slowly approaching the point where it is the only one left.

Just to make sure, take out the wires for cylinders 2 and 6 from the coil pack and start the engine. It should be as bad as it with the wires plugged in.
 

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Here is a good video on troubleshooting the issue. The only issue I see is that you were testing voltage with multimeter and it doesn't actually draw any amps. Maybe you need a noid light to verify the PCM grounding which fires the coil. The vid is for col on plug but still good for your situation. I would disconnect that coil noise suppressor just incase it is draining current to the coil. I had a friend that would not start because on a bad NS.

217899
 

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Discussion Starter · #19 ·
Here is a good video on troubleshooting the issue. The only issue I see is that you were testing voltage with multimeter and it doesn't actually draw any amps. Maybe you need a noid light to verify the PCM grounding which fires the coil. The vid is for col on plug but still good for your situation. I would disconnect that coil noise suppressor just incase it is draining current to the coil. I had a friend that would not start because on a bad NS.

View attachment 217899
i was looking at that thing and wondering if that was it, i noticed the wire coming off the plug from this C shaped thing was bent at a 90 and possibly not getting connection on mine so i straightened it out a bit and looked at the plug. didnt test anything but glad i was looking at right thing. ive never seen one . i do notice that my car is louder and the exhaust sounds differenet so maybe its possible i do have an issue with it. Tmrw im going to pull the 2 and 6 spark plugs out and verify a visual spark from the plugs i guess. and maybe backprobe the coil connector with test light and see if voltage turns on and off with ignition. just need another person to turn the key. idk, im not even sure what to test anymore. this is just mind bending. Im gonna be so screwed if i cant figure this out.
 
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