PCM H5 Codes DTC 301 and DTC 1311

[Scooter G]

This is more for future reference should you throw the following DTC Codes 301 thru 308, and 3111 thru 3118.
We started seeing the 301 & 1311 occasionally show up now & then, and dismissed it and moved on. We'll worry about it later. Then eventually became more frequent over the last week or 2. Yesterday was essentially a limp mode day. Pulled up the codes from the diagnostic manual and the same possible events were listed for both codes.

Could it be as simple as a spark plug?
Yup, pulled #1, and it showed signs of not burning all it's fuel. Other plugs on starboard bank 3,5, & 7 looked like they were burning good.
Back & flying like a rocket ship beast today! Thank goodness for small favors as Grandma used to say.
By the way, these were the original plugs @ 386 hours. How do you know you ask? They had black paint on them below the insulator.

Diagnostic Manual Info:
Misfire is typically a result of one or more factors. These factors can include but may not be limited to: 1) a
fouled or damaged spark plug(s), 2) a damaged or defective ignition coil(s) or coil wire(s) resulting in weak
spark generation, 3) a plugged or contaminated injector(s) that intermittently sticks closed resulting in a
lean cylinder charge, 4) an injector(s) that is stuck open causing an uncontrolled rich cylinder charge, 5) low
fuel supply pressure resulting in multiple lean cylinders, 6) low cylinder compression due to a failed or worn
piston ring(s) or non-seating valve(s) can result in a low cylinder pressure charge that may not be ignited,
and 7) an exhaust leak in close proximity to an exhaust valve permitting uncontrolled amounts of oxygen to
be drawn into a cylinder generating an excessively lean charge either directly resulting in misfire or possibly
causing excessive combustion temperatures resulting in burned valves and loss of compression.




From left to right, bad, good, new





Pretty dang easy to get to

Love how the wires are nembered

Has any one seen where I put my spark plug wire puller? Desperate times make for desperate measures, channel locks will have to do, urgh.
I run a small dab of Dielectric Grease inside the boot, and a small measure of Anti-Seize on the plug threads.
5/8" plug socket, and a magnetic flashlight.


Thought I had a shot of the plug part #, I will update.
NAPA Auto Parts saved me about $40 over dealer and they were in stock.

When searching I found very little info on these codes. Hoping this comes in handy for someone down the road.

See you on the water...

~Scooter G.

[TwinTip]

Scooter, thank you very much for the summary and detailed pictures. Coincidentally, I was just going to post if anyone had some input on these codes. I also have an H5 engine and although the codes are standard, my engine threw a DTC 305 and DTC 1315 recently (I hope the text & codes help anyone for future searches, as I could not find many posts for the H5 or H6 engines). For reference purposes, my engine has 369 hours with orignal spark plugs.

From my searches, some people recommend swapping the ignition coil from the faulty cylinder to another one, then clear the codes. If the fault moves over to the new/swapped cylinder, then it is the ignition coil. Then of course there are the spark plugs, or fuel injectors, that could be causing the fault. The plugs may be the cheapest way to start troubleshooting.

I have not done any work to fix the problem. In my case, I mostly surf and never noticed any misfires. When the faults came up, I was going at faster speeds (20-27 mph). I did notice that there were some misfires, very infrequent, while going faster than at surf speeds and, initially, did not think much of it. Then the alarms came up on the display and I stopped for the day, idled back to the dock. Next day, went out again for surfing only and did not notice any misfires (11.2 mph). I have gone out two more time and no misfires at all. I do have to address this though.

You mentioned a spark plug wire puller. Is there enough space to use a spark plug wire puller? Cylinder 3 seems to have space, cylinder 5 does not. Not sure about the other cylinders (perhaps a question for those that have changed all of the plugs). And while on the plugs, I read that some people recommend just standard car plugs while others suggested the "marine" plugs. And for the purpose of troubleshooting, a car plug would do the trick before spending more on "marine" plugs. As these are not parts that are changed often, I may just buy the PCM plugs (part number I found is: R030013 for both H5 and H6 engines, and gap is 0.040 in. for both engines as well).

Thanks again for the detailed post. This was very helpful.

[Scooter G]

Good stuff TwinTip, and good timing.
My money is on the #5 Plug. Changing coil packs is a major project from what I am able to ascertain, as it requires removal of the exhaust manifold to access. If some one knows differently, please interject, I would love to know a cheat here.
I personally would run with the factory Iridium plugs, NP lists them as part# RP030013, the Auto Parts store will have them tagged as Part# Autolite 41-114. I think I was close to $90 for eight plugs at the parts store. I wouldn't scrimp here, if you mistakenly get into the wrong length or temperature range you may potentially have more expensive reasons to spend money.
You may have noticed that I had thrown the codes 13 times before, started occasionally, and then progressed to ugly.

Sufficient room for plug wire pliers, I ended grapping a cheapish pair of Lyle's at O'Reilys, until my Snap-on's show up (wait, I think I just remembered where I hid them from myself, hmm).
Best of luck, let us know what you come up with...

[TwinTip]

Here is an update on correcting code DTC 305 and DTC 1315.

Even though I noticed the misfire only at higher speeds (20-27 mph), and I usually only surf (11.2 mph), the misfire eventually made it to the slow speeds as well (this is not my area of expertise and I figured this may have to do with rpm's and corresponding voltages). Note that I was able to surf a few times after the original misfire at higher speeds and without any misfires and/or fault alarms. My outings are usually short and two outings ago, I noticed the misfire at 11.2 mph and, initially, no alarms or faults came up. Got to the dock, loaded the boat, and voila, a DTC 305 was triggered (now I have 2 x DTC 305 event logs, as I did not delete the previous logs). I got the PCM spark plugs (RP030013) and decided to first only change #5 (as DTC 305 is for cylinder #5). The original plug was ok, it does not look lean or rich, but changed it anyways. I decided to change this plug only although I did pull plug #3 to compare and they looked the same. This takes me to the last outing (after having replaced plug #5). Initially all was ok and the engine was running smooth, then after a few minutes of the initial start up (getting out of idle and into speed, 11.2 mph) I started to get some misfires. Same as the previous time, I stopped and headed back to the dock. This time I got not other faults.

As I still noticed the misfires, and even though I got no new faults, I am going to be swapping the ignition coil. Unfortunately for this the manifold has to be removed. It does not seem as too difficult. Remove 5 bolts that support the manifold, I think 2 hoses, and 1 sensor. I will swap the coil from #5 with the one from #1 as the #1 coil seems to be accessible with the manifold installed. If the fault moves from 305 to 301 I will know it is the coil and hopefully will not have to remove the manifold again.

My plan is to buy 2 gaskets for the cylinder head (this per the parts manual and diagram attached seems to be item #6, Part No. RM0303) and 2 gaskets for the manifold to corner (item #10, Part No. RM0304). The gaskets are inexpensive. I will need one set of each for the first swap of the coil and may need a second set if I cannot access the #1 coil without removing the manifold (which by then I may need a new coil, hence a new parts order, which could include the second set of gaskets).

If anyone has experience with the removal of the manifold and it is more difficult than it seems, please let me know. Or before I embark on the removal of the manifold, is there anything else that could be causing this (outside of a fuel injector)? Vaccum hoses, fuel pump, etc. I could also buy a new coil wire, which is less expensive than the ignition coil.


Picture #1. Spark plug for cylinder #5.


Picture #2. Example of bolt on cylinder 7 to be removed in order to remove manifold.


Picture #3. Coil on cylinder #1. Seems to be accessible without removing the manifold.


Picture #4. Exhaust Manifold and Components diagram from H5/H6 Parts Manual.


Picture #5. Exhaust Manifold and Components list from H5/H6 Parts Manual.

[Scooter G]

That is unfortunate that the plug changing didn't clean up your problem TwinTip.
I like your plan going forward, so it seems, sometimes you have to throw some spaghetti at the wall until it sticks.
I have found next to nothing on removing the manifolds on these, maybe there is something out there, I couldn't find it. Would love to see your detailed post on this if you go that direction (doesn't sound like you have much choice), next in line is the coil, wire, or injector. My only concern when ripping the manifold is supporting the weight of that beast, it doesn't look light. Maybe a strap and a hoist, or 4 elbows?
I did dump in 2 bottles of Lucas injector cleaner on 30 gallons when I was having my dilemma, ran it on 2 trips before refueling. I don't know, maybe it's snake oil, but my auto parts guru swears by it.
Good luck...

[Rogerabc]

Did you manage to swap coils TwinTip ?
I have misfire on cyl2 on my France based 90 hour 2016 H5 G21 above 2000 rpm.
Changed fuel filter, separator & will try a plug change today.
If it ends up needing coil pack change then I am interested to know whether manifold removal is necessary & if so, how did that go.
Thanks for any advice.

[Rogerabc]

Plug change seems to have cured the problem.