Author Topic: Check Engine Light: Code SPN 3556 FMI7  (Read 13606 times)

Ron Langdon

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Check Engine Light: Code SPN 3556 FMI7
« on: July 31, 2015, 04:28:54 PM »
Last year, (Sept, 2014) check engine light came on with code SPN 3556 FMI7. This week the code has appeared again. Code refers to failure to light ARD (after burner)
Last year the fix was to replace a spark plug with "moderate carbon buildup." At that time, Tech ran tests on system with no negative results. Assumption was that spark plug was the problem. Seems unusual to have the same problem again so soon.
Question: is this common or is it evidence of a larger problem (eg oil in engine,). I want to take it to dealer (10 mile drive) but concerned about possibility of engine shut down. Is this a real concern for that distance or am I overly cautious?
One further note: I did get an intermittent Water in Fuel message a few weeks ago, but been running "fresh" fuel.
Your expert thoughts, please. and thanks in advance.
Engine: Cat C 13, 35,000 miles.

Dave Atherton

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Re: Check Engine Light: Code SPN 3556 FMI7
« Reply #1 on: August 01, 2015, 04:34:09 AM »
Ron, I believe your problem is deeper now a year later failure to light. You indicated soot
last sept. My question did anyone check the inlet section for soot buildup or oil present
on the face of inlet section of DPF filter last sept. What it sounds with your code that soot
buildup on inlet face of DPF filter would have a pressure difference between inlet and outlet
of DPF filter. I would take a strong look at the above along with sensor at ARD Head. It will
not hurt anything to run motorhome 10 miles for repair. One word of advice the cat dealer
has to follow a guide line of EPA on emissions (got feeling the DPF filter was not addressed)
At last repair. last question, have you put injection cleaner in system to keep plug tip clean.
Dave Atherton Retired Cat Mechanic


Ron Langdon

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Re: Check Engine Light: Code SPN 3556 FMI7
« Reply #2 on: August 01, 2015, 05:40:42 AM »
Dave, thanks for your advice. I believe you are correct about the procedure. Last year the focus was pretty much on the ARD. Don't recall discussion re DNF. No, I have not been using a cleaner. If you are suggesting I do, is there a brand you would recommend?
Trucks Northwest is the certified Cat dealer here in Bellingham.
Thanks again

Dave Atherton

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Re: Check Engine Light: Code SPN 3556 FMI7
« Reply #3 on: August 02, 2015, 03:58:35 AM »
Ron. I can provide you with more info. on your C-13 problem. Sometimes the ground for the
igniter to frame is not making continuity another possible thought. Would suggest food for
thought. When Cat looks at unit will get better idea what there thoughts are. If this is the same
Cat dealer that provided your last repair without addressing DPF filter.
Dave Atherton Retired Cat Mechanic

Ron Langdon

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Re: Check Engine Light: Code SPN 3556 FMI7
« Reply #4 on: August 02, 2015, 08:07:46 AM »
Dave, I need some advice about taking the Beaver to this dealer. The techs are all certified by Cat. However they have had trouble changing oil and changing fluid in cooling system. Maybe I've gotten the guys on an off day. Once I give them the fault code, I presume they will follow a check list or procedure established by Cat. To get them to look at the DNR and a loose ground wire might be outside the box for them?
Appreciate your continuing advice.

Dave Atherton

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Re: Check Engine Light: Code SPN 3556 FMI7
« Reply #5 on: August 02, 2015, 12:17:03 PM »
Ron, I think that I would question taking my motorhome to anyone that is ( certified Cat mechanic)
that would have problems changing fluids. What your getting in is not a simple check off list kind
of problem or repair. Never heard of a certified Cat Mechanic except at camping world and that
would not be a likely stop for us. My suggestion take your motorhome to a big Cat dealer that sell
and services heavy Equipment or a big truck shop that works on over roads trucks. I would call
around a little and run some thoughts to each of them and think about what each one has to offer.
This repair can get above very costly if repair shops do not understand Re-gen exhaust system.
Dave Atherton Retired Cat Mechanic

Ron Langdon

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Re: Check Engine Light: Code SPN 3556 FMI7
« Reply #6 on: August 03, 2015, 04:22:02 AM »
the local big cat dealer is who has been servicing my coaches when here in Bellingham.
I have however found another company that services many of the big truck owners and will talk to them tomorrow.
 You have given me plenty of options, and a little heartache. I'm more than a little surprised that an engine with so few miles (35000) is having what could be a serious issue. thanks and I will keep you posted.

Dave Atherton

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Re: Check Engine Light: Code SPN 3556 FMI7
« Reply #7 on: August 03, 2015, 12:36:57 PM »
Ron, you are doing good. Sometimes a person cannot sugar coat problems with different types
of repairs. It seems like us motorhome people have very deep pockets ( repair shop thinking ).
What we hear on the forum poor quality work preformed by inexperience mechanic's many times.
Going to a big truck shop, they deal with this type of repair all the time. What I mentioned earlier
Post with re-gen problem at 35,000 miles again sounds like a sensor failed to light as per post
and suggest the upper sensor is the problem. A experience service tech standard repair will
open up the DPF filter housing looking for the soot and oil on the inlet face and temp difference
Between inlet and outlet of DPF filter, than tubing on DPF housing, check ARD head. Again I
suspect the problem is the upper sensor. There should be 3 sensors on your system. This gives
You a over view of problem without going deep in technical talk.
Dave Atherton Retired Cat Mechanic

Ron Langdon

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Re: Check Engine Light: Code SPN 3556 FMI7
« Reply #8 on: August 08, 2015, 04:56:14 PM »
Dave, once again thanks for your advice. here is the latest twist. Apparently I have an "old" air based regen system. Service mgr called Cat and it was recommended that my old system be replaced with the new heat based system. I meet with service mgr on Monday. To the uneducated, (me), this sounds like the diesel version of electric problem solving--replace the board. This of course will be at my expense, not cat's. What do you recommend?

Dave Atherton

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Re: Check Engine Light: Code SPN 3556 FMI7
« Reply #9 on: August 08, 2015, 06:56:46 PM »
Ron, first what did they do to determine up date the board. Funny I have several inquiry's with
your code and you are the first one to bring out the update board. Would suggest what is the cost
going to be and second if that does not correct problem do you have to still buy the update board.
our last post did they start and go through system starting DPF filter inlet for soot and oil and outlet
end. Did they determine the heat at both inlet and outlet. Did you yourself look at the end of your
exhaust pipe ? Soot, pipe clean, smoke at start. I would suggest it sounds like they might be throwing
parts at system but if it is on your dollar I would ask what is there game plan. simple thing as the new spark plug or not grounding. It is again a honest question, did they do a complete troubleshooting I'm
kinda not buying into the new board because once they put it on it's yours. Will pull up your system and see if there is something I can help with. Dave Atherton Retired Cat Mechanic

Dave Atherton

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Re: Check Engine Light: Code SPN 3556 FMI7
« Reply #10 on: August 08, 2015, 07:15:45 PM »
Ron, back again. First contact problem spark plug soot up. Pulled up some info.that might help.

Spark plug is fouled : problem with the ignition wire between ignition coil and spark plug.
Problem usually occur because the ignition wire has been damaged by excessive heat or
improper routing.

Ignition coil has a problem.
Dave Atherton Retired Cat Mechanic

Ron Langdon

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Re: Check Engine Light: Code SPN 3556 FMI7
« Reply #11 on: August 09, 2015, 05:35:07 AM »
Thanks again, Dave. When I meet with them on Monday morning, I will have all these items on a list to be sure I don't miss any AND that they have completed the list. I tend to want to resist the new board suggestion, unless all else proves a need for it. Interesting that others with this code aren't getting new boards.
Talk to you later and thanks again.