So I have this MIL code that won't go away.......

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SargeW

SargeW

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I have had a MIL light and trouble code come on a few times in the last few months. It has gone gone off and on a few times, but has not stayed on for very long. Then it was gone for about a month, but it came back about 2 weeks ago, and now it won't go off. I did have a few random codes that would come and go, nothing remained on for very long.

The code that won't go away is SPN 4342 FMI 3. I tried running the code on my Cummins Quick Serve phone app, and after in putting my ESN and entering the code, I get "Aftertreatment 1 Diesel Exhaust Fluid Temperature 2- Abnormal Rate of Change.

Not sure what that means, but the coach is still running like normal, and the code still shows as Active when I check the fault codes in the digital display.

I have tried all the rest procedures, but none have cleared the code. I called Tiffin customer service and spoke to a tech. He recommended turning off the chassis battery switch for a few minutes, then turning it back on and starting the coach. Nope, no love.

Anyone have a clue what the code means in plain English?

I am supposed to get a call back from a different tech tomorrow and maybe get some more info.
 
You most likely need to speak with Cummins, as it is related to the engine. The DEF system can be a nightmare. It can set codes due to a faulty sensor. Or there really could be a problem. The code has to do with the DEF line heater, measured at an exhaust bank.

Cummins will most likely have to clear the code. It is best if the code is still present when they hook up to it.

Depending on the severity of the code, in some instances ignoring a code will cause the engine to de-rate. It will start at say 10% de-rate, then to 25%, and continue until the engine will eventually shut down. It may take 500 miles for the engine to shut down. Again, it depends on the severity of the code.

Disconnecting the battery will not reset codes.

 
When I first read the title to this post Marty, I thought is was going to be about your Mother-In-Law.  (MIL)  :eek: ::) ;D
 
Well, I have had a few "mother-in-laws" that would apply to Rene! But I am fresh out at the time. I did make an appointment with a Cummins dealer in La Jolla, for early this coming week.  It sounds like a sensor issue of some sort. Gotta plug it in to find out.
 
So the stubborn MIL light was resolved today. I took the coach to Cummins Pacific, in El Cajon, Ca. Nice facility BTW. The service supervisor, Robert, very nice knowledgeable guy. I noticed when I pulled into the lot that there were several other RV's there.  I asked him during the check in process, "so, do you do many RV's here?".  And his answer made me even more  comfortable. "Oh yeah. All day, every day!" 

So a long story short, they took it in and verified the MIL code that my  VMSpc had been alarming for the last few weeks, and started looking for the reason. In checking the voltages on the concerned wires that controlled the heat on the DEF lines, all three lines should have registered 5 volts on the VOM.  Two did, one showed 0 volts. In tracing the rather long length of the wire they found that one of the electric supply wires for the DEF heater had pulled loose and was laying against the fan clutch of the radiator cooling fan.  It took 6 months,  but the fan had finally wore through the wire, severing the connection. That explained the intermittent MIL leading up to the constantly displayed MIL. 

The below pic is the section of the wire that the tech cut out and repaired the wire with new connectors and heat shrink.

So it cost me a little time, (as Tiffin stepped up with warranty approval) but now all is back to normal, and the Journey continues!
 

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What a coincidence! I was just going to suggest that you check the continuity of all three 5 volt lines to the DEF temperature sensors. :) Really glad you got it fixed Marty.

Kev
 
Rene T said:
When I first read the title to this post Marty, I thought is was going to be about your Mother-In-Law.  (MIL)  :eek: ::) ;D
Click to expand...

Yeah, title definitely made me think about my MIL who's lived with me and the DW for the last 12 years.  Glad you got it fixed, Marty.
 
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