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Code P0351, coils?

Tiny
SHERI ALLEN
  • MEMBER
  • 2012 FORD F-150
  • 5.0L
  • V8
  • 4WD
  • AUTOMATIC
  • 232,000 MILES
My truck keeps throwing the P0351 code even after changing the coil multiple times. It’s the only code the truck is showing. After clearing the code runs great for about 30 miles then starts missing vibrating and the P0351 comes back on? Please, this is getting expensive to keep throwing coils at it, it also has new OEM plugs.
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Thursday, March 23rd, 2023 AT 5:35 PM

23 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

The code is certainly coil related, but it doesn't indicate a bad coil. When this DTC is set, the PCM enters failure mode effects management (FMEM) which shuts down the injector for the associated cylinder in order to protect the catalytic converter.

The cause can be a few things. However, most commonly, we have a wiring issue. Here is what I need you to do first:

Use the 12-volt non-powered test lamp to verify the Start/Run key positions voltage at the ignition coil harness connector.

Disconnect the cylinder 1 coil pack. There should be two wires present, one is violet and the other is white with a violet tracer.

With the key in the run position (engine off), the violet wire should have power at all times. Confirm that for me.

If that is good, place the alligator clip of the test lamp on the positive battery terminal and probe the white wire with the violet tracer. Have a person crank the engine. The test lamp should strobe on and off.

Do this and let me know the results.

Take care,

Joe

See pic below.
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Thursday, March 23rd, 2023 AT 7:07 PM
Tiny
SHERI ALLEN
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  • 36 POSTS
Thank you so much. We will do this as soon as we get home or first thing in the morning. It’s kind of cold out here now. I will keep you updated. Thank you.
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Thursday, March 23rd, 2023 AT 8:05 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

You are very welcome. When you can, let me know the results.

Take care,

Joe
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Friday, March 24th, 2023 AT 9:58 PM
Tiny
SHERI ALLEN
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  • 36 POSTS
My truck has power to the violet wire when tested the white with violet no strobe and truck started like normal with the coil off now what? Thank you
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Saturday, March 25th, 2023 AT 9:43 AM
Tiny
SHERI ALLEN
  • MEMBER
  • 36 POSTS
I have no power to the white with violet wire going to the number 1 coil, any suggestions?
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Saturday, March 25th, 2023 AT 6:26 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

the white/violet goes to the PCM. The PCM provides a ground path that completes the circuit. If you had the alligator clip of the test lamp connected to the positive side of the battery and the other end to the white/violet wire, it should strobe (while cranking) when the PCM completes the circuit.

Is there any evidence of wire damage? Let me know. We may need to check at the PCM itself for the ground path.

Let me know.

Joe
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Saturday, March 25th, 2023 AT 9:26 PM
Tiny
SHERI ALLEN
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  • 36 POSTS
No the wires look okay, but there is no strobe effect on that wire.
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Sunday, March 26th, 2023 AT 12:28 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

Okay, we need to go to the PCM to see if the ground path is present there. It could be something as simple as a broken wire or pin at the connector, or the PCM may have failed.

Pic 1 shows the white/violet wire at the PCM. Pic 2 confirms it is pin 70 in the black PCM connector. Pic 3 shows the pin location. I need you to disconnect the connector and inspect it for corrosion or damage on pin 70.

If that is good, then we need to probe that connector and see if the test lamp strobes at the PCM. If it doesn't, the PCM is my primary suspect.

Note: I always recommend the battery gets disconnected anytime the PCM is being disconnected or reconnected.

Let me know what you find.

Joe

See pics below.
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Sunday, March 26th, 2023 AT 8:26 PM
Tiny
SHERI ALLEN
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  • 36 POSTS
Okay, we have strove on white with violet wire truck is still throwing PO351 code and missing vibrating when code is thrown, I’m at a loss with this truck.
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Tuesday, March 28th, 2023 AT 10:22 AM
Tiny
SHERI ALLEN
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Another question for you, my gas mileage is 19.6. That’s as good as it was when I bought the truck. If it’s still missing and not driving really well, why is my gas mileage so good?
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Tuesday, March 28th, 2023 AT 1:50 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

If the PCM provides a ground path and we have constant voltage to the violet wire, that leaves a coil issue, plug, or poor connection.

To get the strobe, did you get it at the PCM or the coil pack?

Joe
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Tuesday, March 28th, 2023 AT 8:38 PM
Tiny
SHERI ALLEN
  • MEMBER
  • 36 POSTS
Coil pack.
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Wednesday, March 29th, 2023 AT 6:50 AM
Tiny
JACOBANDNICKOLAS
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Hi,

That is a good thing. Check the connector to the coil to make sure nothing is damaged. If that is good, switch that coil pack with a coil from a different cylinder. Clear the codes and see if the misfire returns to the same cylinder or if it changes.

It sounds like you may just have a failing coil.

Let me know.

Joe
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Wednesday, March 29th, 2023 AT 7:00 PM
Tiny
SHERI ALLEN
  • MEMBER
  • 36 POSTS
We changed out the coil and it ran for about 80 miles with no issue with check engine light. Now today it tripped again the only other issue now is it vibrates shimmy’s until we hit about 65 MPH then it smooths out. That was before the light came back on that and it says my gas mileage is at 19.6. When the engine light is on and when it’s off no issue. My mileage is at 11.6 weird.
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Friday, March 31st, 2023 AT 8:15 PM
Tiny
JACOBANDNICKOLAS
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Hi,

That is odd with the fuel mileage. Have you checked to see if the code has changed since the coil was replaced?

Let me know.

Joe
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Friday, March 31st, 2023 AT 10:40 PM
Tiny
SHERI ALLEN
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Same code PO351
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Saturday, April 1st, 2023 AT 12:19 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

Okay, the mileage makes no sense to me. Since it is the same code, we should check compression to see if it is low in that cylinder. Either we have low compression in that cylinder or there is an injector problem. If it ran good for that many miles without issue and then returned, it is specific to that cylinder. The only other thing I can think of is if you lose power or the ground path intermittently for the coil. However, you indicated the connectors are in good condition both at the coil and PCM, correct?

Here is a link explaining how to check compression. You will need a compression gauge, but most parts stores will lend one to you.

https://www.2carpros.com/articles/how-to-test-engine-compression

Let me know your thoughts and questions.

Take care,

Joe
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Saturday, April 1st, 2023 AT 2:39 PM
Tiny
SHERI ALLEN
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Thank you. I’ll check compression as soon as I can get to town, I live out in the boonies, lol.
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Saturday, April 1st, 2023 AT 10:17 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

No problem. I live in the country but wish I was out further. LOL Take care and I'll watch for your reply.

Joe
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Sunday, April 2nd, 2023 AT 5:54 PM
Tiny
SHERI ALLEN
  • MEMBER
  • 36 POSTS
I’ve got a real problem now, the intermittent coil issue, but my windows stopped working. So, I was in the truck most of the day trying to figure them out, I have power all the way to the motor and then nothing okay fine. We’ll I drained the battery in the truck I guess from having the doors open we’ll when I went to jump it put the positive cable on first then went to attach the negative cable and it almost drained my other truck and sparked. So, I must have done something messed up looking for my window wires inside the door, how can that be? I think electrical issues bug time, yeah.
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Sunday, April 2nd, 2023 AT 6:00 PM

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