I have been fighting a check engine light that has kept throwing a P0355 Ignition Coil E Primary/ Secondary Circuit fault. No other codes.

After reading up on the code I figured it was either a coil pack, harness or module issue.

I replaced the #5 coil pack. Same issue. I traced the wires from the coil pack to the module and found no issues. I was about to price a new module but decided to see what the Ford dealer ship would say or diagnose.


After taking it to them, they told me the truck had two codes, P0305 and P0306. These are specific to the #5 and number #6 coils. They did a compression test and swapped coils from known good cylinders. Turns out the issue was the spark plugs.

I asked about the code I got and they stated Ford F150's do not have such a code (P0355). We looked thru the manuals and computer and could not find anything.

So long story short, apparently, diagnostic tools such as my Inova Scan tool and placed like autozone or Firestone do not read codes the same way the dealer tools do.

I spent weeks chasing a ghost due to a code that doesn't exist!

 

http://www.troublecodes.net/pcodes/p0355/

Basically they are pissing on your leg and calling it rain. That code is very real.

If they are saying the spark plug is the cause they are lying again, here is a ss of the exact test procedure from the Ford shop manual. They created a story of some sort of serious or oddball repair to save face that they just threw some parts at it to repair because they don't know how to properly diagnose the concern, find a new shop to take your truck to.


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Interesting and colorful opinion... THANK YOU for the info you shared though, I saw some of the same info when I was diagnosing the issue as I have the OEM shop manual, just not the special diagnosis tools.

I would have to disagree only because in this case it would not be in their best interest to do so.

My scan tool (as did auto zones) definitely read the code. And maybe the dealer is mistaken that the code does not exist on for the F150, but I'm not sure of what their motivation to lie would be or why the cause turned out to be a spark plug.

Prior to this trip to the dealer, I was chasing other more obvious codes for plugs. I attempted to replace the plugs, but when the first plug went "crunch" as I attempted to remove it. I cut my losses and took it to the dealer to have them replace all 8 plugs. I did have them do some troubleshooting (compression test etc..) while they had it and it all checked out fine. After the plugs were replaced I turned off the check engine light and drove home with the new plugs. The vibration was still there. Shortly after the check engine light came back on with the P0355 code. This was not the same as the previous codes.

So when I gave up and took it to them for this, fully willing to pay the $110 diagnostic plus repair, they told me the story in my original post. They didn't see the P0355 code at all, but two misfire coded P0305 & 306. They did all the checks and it came back to the bad plugs. They replaced the plugs, reset the light and the issue is 100% gone.

Further more, they charged me NOTHING. They said it may have been their fault and that the plugs may have been damaged or cracked during install.

If they were being dishonest, they could have sold me a new module and new harness to correct my P0355 code....

 

Yes, well I wasn't extrapolating on the $$ side, more so to the embarrassment side of them not knowing the proper procedures. Glad you got it fixed in any event.
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