P0305/PCM question

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Dec 17, 2024 | 09:50 AM

colorado_junkie

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5th Wheeling

Joined: Apr 2015

Posts: 26

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From: Colorado

P0305/PCM question

Good morning everyone. I started my 2011 3.5L Ecoboost this morning and the CEL came on instantly. After letting the truck warm up a minute or two I started to drive over to O'Reilly's to have the code read. Right away I can feel something was wrong and the CEL started blinking. The engine code was P0305, which I am no stranger to. Now, my question is....when the O'Reilly's report says Permanent (taken with a grain of salt) does that mean the PCM is bad and needs replaced or can the codes be cleared by Ford and keep the PCM? Reason I ask is I recently had a 2008 Ford Taurus that had this exact same issue and the local Ford dealership gave me an expensive run around, telling me the PCM was bad and needed replaced. Thanks in advance for any thoughts/suggestions.

Dec 17, 2024 | 11:15 AM

RLXXI

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Joined: Nov 2020

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From: Sportsman's Paradise

Quote:

Originally Posted by colorado_junkie

That code is cylinder 5 misfire. Had nothing to do with the pcm. Permanent code just means the pcm had to clear the code on its own once it sees the misfire fixed. Could be coil, plug, injector base engine. Need to run some diag on it to be sure.

Dec 17, 2024 | 11:50 AM

colorado_junkie

Thread Starter

5th Wheeling

Joined: Apr 2015

Posts: 26

Likes: 1

From: Colorado

So, theoretically, if I change coil, plug and/or injector and the CEL stays on with the same code would that determine the PCM to be bad? Just looking forward to my next steps if needed. I'm a desk jockey so I can't get to the truck till this evening. My plugs and coil packs are at ~30,000 miles right now so I'm a bit surprised to see this code.

Dec 17, 2024 | 01:53 PM

RLXXI

Lead Driver

Joined: Nov 2020

Posts: 7,128

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From: Sportsman's Paradise

Quote:

Originally Posted by colorado_junkie

I don't deal in hypotheticals or theories, I deal with cold hard facts and the only way to get them is to put hands on and diag the machine. Could also be critter damage, rats/squirrels like to make nests around a warm engine in the winter and love to gnaw on wiring.

Give it a good look over, may need a borescope to get eyes on some of the harness under the intake manifold. If you don't see any physical damage then it's time to get deep into diag and that requires special tools/equipment/knowledge. Forced induction engines are notoriously hard on everything especially spark plugs. 30k miles is not unheard of for a plug to go bad on that engine.

Also if you used anything other than Motorcraft/Ford plugs/coils, you likely found the problem.