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Old 05-23-2022, 01:37 PM   #1
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Possible DEF Head Failure

Please forgive me if this is posted elsewhere, I did a search but was unable to find a relevant thread. We have a 2020 Newmar 4369 Dutch Star. We just returned from a short trip within the state we live in, Florida. Upon moving the coach this past weekend to wash it (love bugs splattered on the front end) I noticed a "check engine" light and "LOW DEF" indicator light. However, DEF is at 40%, so not low. I fear we may have the dreaded DEF head failure. I've read that it is possible to clear the warning by disconnecting the DEF head, waiting a few minutes and plug it back in. Also read that using a code reader can do a similar clearing of the errors, however the socket under the dash is NOT the typical OBDII, it is a round socket receptacle which is simply labeled "OBD". I'm pretty sure getting a replacement DEF head (Gen 7) could take many months, in which case our RV is grounded for a while. Any advice? Thank you.
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Old 05-23-2022, 02:13 PM   #2
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Youíre right, the plug is NOT OBDII itís J1939 like most semi trucks. Very possible the DEF Head is starting to fail. Trying to clear codes will only work if the fault is no longer present. Some have reported that DEF head are more available now, but who knows until you get to a shop. Based on your coach year, itís probably under warranty.

Also you may want to look at this:
2020 Tiffin Allegro RED340 33AL
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Old 05-23-2022, 03:52 PM   #3
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Before you go too crazy, I would add DEF first. At 44%, it could be triggering the low DEF light.
Don & Mary
2019 Newmar Dutch Star 4018 (Freightliner)
2019 Ford Raptor
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Old 05-23-2022, 05:15 PM   #4
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Hi @Dutch Star Don and David and Wes. I agree with DSD. The fact that the actual data being reported is 44% makes me believe that the sensor is reporting correctly. With the type of failure that the Sensor normally shows, there would be no data at all or a nonsense quantity.
2021 Entegra Aspire 44W
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Old 05-23-2022, 05:41 PM   #5
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The good news is you have a Freightliner, and their DEF sensors have proven far more reliable than the inferior Shaw systems used in Spartans. Furthermore, worst case, Freightliner DEF header availability isn’t an issue.
2021 DSDP 4326 Freightliner
2005 KSDP 3910 Spartan
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Old 05-24-2022, 07:46 AM   #6
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Thank you Dutch Star Don: I added another 2.5 gal DEF container to it yesterday, gauge did not show any increase, maybe a stuck float?
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