The coils have been going bad one after the other, so I went ahead and replaced all of them. Now I’m getting P0356. I’ve swapped the coils around and it’s still there. I don’t see any issues with wiring. I don’t know what else I should do. Any advice would be appreciated.

 

In 25 years and three Ford V8s with coil on plug and I've had ONE coil go bad. Something is wrong!

 

The code 356 tells you cylinder 6 Coil Primary circuit between the PCM and the Coil is open circuited, shorted to ground, or the coil primary is open.
A PCM coil driver could also be the cause.
Do some testing with a meter to be sure Coil voltage is present at the connector Ignition On, the ground from the PCM is occurring by looking at the coil to PCM side with a meter set to 12 volts and seeing it pulse, as the ground from the PCM is applied while running at Idle.
Don't look anywhere else but for this Ground fault from the PCM.
If you don't see it pulse, either the wire back is open at some point or the PCM is faulty.
Another way to test is set meter to 10k Resistance and test for a ground coming from the PCM, engine off Ignition Off, Coil connector off, meter Neg to ground connector lead side.
A good reading will be in the 10k range + /- , No very low or very High reading is acceptable with the Connector OFF the Coil.
Test another good Cylinder to see a what value you should see.
Good luck.

 

Can I ask here too?
I am battling a similar (same) trouble.
I have a 2009 Lincoln MKX with 3.5 v6.
Driving to work last week it started missing.
Originally showed P0306.
Thought I could swap plug and/or coil and be set.
Not yet
I have tried multiple plugs and coils, inspected connections and wiring, but seeing P0356 now and has the miss.
Suspicious of the PCM, but hate to do anything with it not knowing for sure.
Wondering if I can ask some stuff for my own clarification that would help me know what I have happening.
Right now I have seen a few "videos" and sites showing how to check a coil with OHM meter.
Don't think that is the issue because I have tried 4 used (were running OK when pulled) and 1 brand new.
I have pretty limited electrical knowledge so am asking for what some might see as elementary questions.
I saw that you could OHM test across the two coil connections to see if primary circuit is OK.
I am using a Klein meter like shown below.
My red and black leads are placed as shown in pic too.
I tried 2k 20k 200k and 2M settings there.
Saw .4-2.0 ohms should be shown.
Also see that checking across one input connection and the spark plug side can check secondary side.
I found 5-20 thousand ohms there.
Wondering if I am doing that correct, just to let me level of knowledge out here.
And on the car checking the connector that plugs into coil-I see 12+ volts (battery voltage-12.3 with key ON, 14 with engine running) and ground on other side.
I am fearing PCM bad, because I also had a LOT of other show up shortly after that, that made me think alternator overcharged (ABS, check battery, traction control).
So, you write about "Do some testing with a meter to be sure Coil voltage is present at the connector Ignition On" does that sound like me seeing 12 with key on like I think?
AND...
"If you don't see it pulse, either the wire back is open at some point or the PCM is faulty" I have seen ground (solid) on the other side of the coil's connector.
I should see a pulse with engine running?
If not either broken wire, bad connection somehow, or bad PCM?
Any other info on checking PCM?
Pin # and connector location I can check?
As far as the "other" test:
"Another way to test is set meter to 10k Resistance and test for a ground coming from the PCM, engine off Ignition Off, Coil connector off, meter Neg to ground connector lead side.
A good reading will be in the 10k range + /- , No very low or very High reading is acceptable with the Connector OFF the Coil."
Is that going across both coil connector posts, OHMs still on meter, set at 20K?
Red and black lead plugged same spots?
And everything I have compared to #5 cylinder has been same so far as I can tell.
I have not tried pulling coil connection on another cylinder yet while running/only with key on, since not sure if just 4 with chug along...
REALLY appreciate whatever I can find out
Can use all the help I can get.
Worst case, any info on PCM replacing?
I see they have to be programmed for VIN.
I do have a TopDon ProScan bi-directional OBD scanner tool if that will let me do anything like that.

BIG THANKS

 

If you have a solid ground coming from the PCM, it powers the coil full time because there is 12 volts on coil when ignition is on. and can't pulse for spark when commanded to do so, in the fire order. Hint is if the coil gets warm with Ignition on for awhile since it will draw about 7 amps. With engine runnig you should sevoltage pulsing on your meter when engine is running, same as on a good cylinder's coil.
Either lead is grounded or the PCM has a fault.
Unplug at the PCM to see if the ground goes away. If no, the lead is grounded. If yes, the PCM has a fault.
This is for the 356 code that is an electrical fault code
306 code of only for coil secondary, boot, plug or cylinder issue. This code sets when cylinder loses combustion power and crank rotation is a longer measured rotation interval.
Grounded coil from PCM to coil, nothing works.
Good luck.

 

There is a DIAGNOSTIC SEQUENCE to follow in the 2009 LINC WSM.

Do you have that info?

 

Sounds like I have another check to do then, THANK YOU !!
I will check for pulse now.
The P0306 was early in the morning drive.
Then it has been P0356 since.
Appreciate the help and advice.

 

I do not.
Have been searching online and asking where I know folks smarter than myself hang out.

 

Tried a few more checks tonight.
Compared #5 and #6.
Both seem same as far as I can tell.
Battery voltage on one side of the coil connectors with key on.
Running about 15.1 at both.
(I did use a test light one the coil connector's weather pack 1st side-alligator clip on negative battery terminal-probe tip 1st side connection)-it lit solid with key on and running)
The other side had ground with key on, I was putting my meter's red lead on the positive battery terminal and black in coil connection, reversed from the first set up.
Running, I thought there was 15 volts steady at both.
But watched, looked closer it looked like my meter just wasn't reacting fast enough (I am guessing).
I was thinking I could use a test light/probe and watch for flashing light, but the second side of coil connection wouldn't light it up at all.
(That was with alligator clip on positive battery terminal, probe tip into the weather pack's "2nd" side)
With meter saw reading dropped down to 11.--- back up to 15.
Whatever it was doing, it was the same on both of those cylinders.
Only code again was/is P0356 "F".
Had been wondering/worrying it was PCM before seeing both acting the same, now I do not know what it could be besides coil and/or plug.
BUT I have tried 3 different plugs and 5 different coils now.
Think I will swap both plug and coil from 5 to 6 - just do not know what else to do or what could be going on.

 

I took my new coil into work with me this morning.
Sat at my desk and tried the ohm meter tests that I had read about.
Had resistance between the two "input" connections (primary).
But nothing when checking between either "input" and the spark plug "output" connection (secondary).

 

You might find more help at a LINC SPECIFIC FORUM - https://lincolnmkxforum.com/

Without factory repair info or an experienced TECH it is going to be a crap-shoot as to what info you will find.

Let the board know what you find.

 

THANK YOU VERY MUCH !!
I will do some searching and see what I can find !
Appreciate that !!

 

Just do NOT know why this is such a pain.
Got 6 new coils and plugs delivered.
Sat at work this morning OHM testing them all.
Trying to figure out if I am doing the test wrong, or what ???
All test same.
Shows less than an Ohm on primary side, but EVERY one I have tested so far is open secondary.
What am I missing?
Are coils DOA and junk that often??
This brings total I have tested bad to 12 I think.
Some old ones that I thought were good when pulled.
7 new.
Guessing my next step will be pulling cylinder 4 or 5 which seem to running OK, and see what they show.
Would not guess nearly that many new parts would be bad, but seems to be "popular" in online reviews.
I know that I do not have the best luck, nothing is easy (but thought this should be), and it is way too COLD for all this.

 

How are you measuring the secondary resistance? It should have very high resistance compared to the primary, so make sure your ohm meter is set on its highest scale.

But that's not the best test of an ignition coil. It may show correct resistance with a static measurement, but when it's active, it generates very high voltages on the secondary that can jump through weak or damaged insulation that offers less resistance than the gap on a spark plug. You MAY be able to find that with a capacitance meter, but not very likely.

 

I was wondering if I was doing anything correctly.
I mirrored what I saw on a LOT of You Tube videos.
Everything looked similar to what I was doing, EXCEPT the videos all showed resistance, I see OPEN.
???
This whole deal has been FAR more of an ordeal than I ever would have imagined.
I bought this car about 3 years ago, next day a coil failed.
Wasn't a huge deal.
I learned about pulling the intake for back 3.
Replaced all the plugs and coils was good for 2 1/2 years.
Just about a year ago IIRC one showed misfire.
That was a rear bank too, but still had 5 of the coils that I removed and swapped one of those in.
Now # 6 front side shows misfire.
Thought, "here we go again" not a big deal.
Have tried all the parts I had on hand, one new coil so far, and played musical chairs swapping stuff around and checking.
Thinking I am really investigating now and making sure that there is NO WAY I am putting in a DOA new coil after all this.
But here I am with these checks, not seeing anything that tells me what is good vs bad-all the new stuff seems bad according to what I am seeing online.
AND...it's FREEZING right now.
More than a few minutes in garage is all I can take.
So, I will try some more parts, swapping, tests, checks, trial and error, see where I am, and report my news just in case anyone else can get anything out of it beyond blah, blah, blah, and/or humorous entertainment

Thanks the input, feedback, and assistance (need all I can get)