Hi,
I just started to get a misfire. I had the code checked at Auto Zone and it showed a P0354 Ignition Coil D Primary/Secondary Circuit Malfunction.

I did a search and it pulled up one helpful article saying it could be the wire going to the coil could have shorted on the AC hose. Made sense and it seemed to be the fix for a number of people. I checked quickly and didn't see any bare wires and felt them and it felt ok...no melted or torn wire insulation.

I understand the Primary circuit is between the PCM and the coil, and the secondary circuit is coil to plug. Since it is saying it could be the secondary circuit, that could be a coil pack, right?

Any help would be great. It's 6 degrees up here today, so if I'm going to be wrenching on my car, I'd like it to be time well spent!

Thanks.

 

I think you are on the right track.
The miss could be a coil or a spark plug.


Richard

 

It was the coil. Problem solved!

Now, do I have to go to the dealer/auto parts store to get the Check Engine light off?!?

 

One other tidbit to pass along that I found out last night...I was told that Accel coils have no warranty...I went to their website and found that they have a 90-day warranty. That really shocked me and made me not get them.

I opted for the Auto Zone branded coils with the 3-year warranty. I figure if I have to do this again, the parts might as well be free.

 

Good to know about the coil warranties. Thanks for posting that.


You don't need to see a dealer to clear the engine trouble light. Most scanners will clear any codes that are stored in your PCM. On some types of problems the engine trouble light will eventually go off after a certain number of driving cycles. But the fact that you had that trouble code will still be stored in memory in the PCM.


Auto Zone does or used to (not sure) scan customers PCM for free. If so they could clear all the codes. If you have a friend with a scanner or a friendly garage could clear the codes for you.


Some codes, such as anti-lock brake systems will not clear until a repair has been completed.
I'm not a professional mechanic. However I have worked on cars since the 1950's.
Richard

 

I just had the very same issue, needed a new coil on the #7.

Is it likely that the other coils will star failing too? Should I replace them all to get ahead of the game or is this just a rare thing on these 5.4 motors?

 

I'm no expert but if I was really worried that a coil failure would cause me a serious disruption then I would have a spare. I am retired with two cars so I don't worry about it. I do think a coil failure is not rare but not immanent either.
I have a 2007 Navigator with 65,000 miles on it and have had no coil failures. I would not be shocked if I have a coil failure someday.


My daughter had a 2000 Mercury Sable V6 that had coils on each spark plug. After about 100,000 miles she had 2 or 3 coils fail over a period of about 3 years. She put 230,000 miles on the remaining coils. After the first failure I was better at diagnosing when a coil had failed.


I could see hairline cracks in the insulation on the coil tops but that did not always cause a failure.


Richard