peterbilt 579 MX13 code P3937

Discussion in 'Peterbilt Forum' started by Arctic_fox, Apr 24, 2021.

  1. Arctic_fox

    Arctic_fox Medium Load Member

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    So i was driving today and had my truck throw code P3937 at me which google says the ECU actuator temp is out of range high. Any idea what would be causeing this? never seen this code before. Just had a nox sensor replaced as well.
     
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  3. AModelCat

    AModelCat Road Train Member

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    Google tells me its a DEF quality fault.

    After a certain year an actual sensor in the tank was required. Earlier years based it off the NOx reduction through the catalyst. Having had a NOx sensor replaced makes me question if it was correctly installed. Maybe requires a calibration?
     
    spsauerland Thanks this.
  4. Arctic_fox

    Arctic_fox Medium Load Member

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    Perhaps? i know the actual dealer did it so it "should" be good. As for def quality i use jugs and haven't added any recently so unless the jug was bad im unsure. My davie4 wont clear the code though
     
  5. spsauerland

    spsauerland Road Train Member

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    Screenshot_20210424-140906.png
    Is it an EPA13 or 17? Most likely issue with DEF QLS in the tank. Tank heater coolant control valves have been known to be route cause of of the DEF QLS failure. Is code active or inactive (red or orange)?
     
    062 Thanks this.
  6. GYPSY65

    GYPSY65 Medium Load Member

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    What year truck?

    My previous 2014 Mx started going through sensors and I had them replaced a couple times under warranty
    It finally shut me down in Ogden Utah
    KW shop there dumped the def and flushed the egr cooler

    They said they have guys who do those two things and a filter burn every fall and are never down
    Don’t remember if they did the burn as often or not on that
     
  7. Arctic_fox

    Arctic_fox Medium Load Member

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    Sep 16, 2016
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    Sorry for lack of info i was a tad distracted and midly paniced earlier trying to figure out why my truck was being stuborn.....again. Its a 2017 579 with i am 99% sure an EPA17 MX13 engine in it.

    @spsauerland Id love a link to a better fault code list if you have one. My tool only gives me the fault code, engine stats and lets me do a regen. It doesnt tell me too much beyond that. The google link i used earlier gave me a list with apparently incorrect info.

    Anyway I used a siphon and 5 gallon bucket to drain and refill my def tank with new def and the issue went away after a few miles. My guess is i maybe got a old jug of def at the ma and pa i stopped at? It was pretty dust covered and nasty plus the lady was suprised i bought it.... so eh working theroy until a more serious issue pops up.

    As for the fault it WAS red and now is orange. and allowed me to log and clear it on my laptop. Ill see about haveing the tank purged then cleaned and the egr cooler cleaned again. I know they cleaned said cooler according to my paperwork when they did the nox sensor as part of the warranty work on the nox sensor, but better safe then sorry.

    Anything else i should check to ensure its not an up or downflow problem? Ive only had the truck a couple months and considering the number of gremlins ive throttled so far...... i am just going to assume the truck was either poorly maintained or they stopped doing it prior to sale as a "not my problem" thing.
     
    GYPSY65 Thanks this.
  8. GYPSY65

    GYPSY65 Medium Load Member

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    When I had an issue they took the def tank off and drained and cleaned it well

    Not sure if fuel tanks would be an issue but if you’re draining a d cleaning maybe hit those if. It sure on how well it was maintained
    I wouldn’t drain and remove. Maybe just drain some off the bottom via the plug??
     
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