ISB6.7 DEF HELP

[lastmanstandin31]

(01-21-2021 )JimT Wrote:  

(01-20-2021 )lastmanstandin31 Wrote:  Problem is def system will not prime half the time and throws pressure codes and def input line codes every day which derates the truck. I

Sounds like you know where the problem lies, it's just a matter of going over those parts until you find the cause. Either the pump isn't doing it's job or there's a line or fitting leaking. Also, double check the filter. it's really easy to NOT get it seated properly and therefore the cover won't seal properly.

When you say you replaced "doser unit" do you mean the doser valve mounted to the decomp tube or are you referring to the pumping unit? What about sensors in the DEF system? Maybe a bad pressure sensor? If someone put paint in there I'd be suspicious of any rubber seal or o-ring. Could also be something inside the DEF tank itself.

Yes it was the doser valve on decomp tube. The pressure sensor is part of the doser valve, that is part of the reason I replaced it. If the truck is here at my shop it will pass the bypass test, leak test and even do a parked regen. Its when we are actually driving the truck that the doser input line code comes along and shortly after the 5mph derate comes. When it does this the only thing I have found to clear the codes so I can drive it back to the shop is using insite to flash the incal calibration file to it and then it drives back to the no codes or anything untill I drive it around our parking lot for a hour or so then the code comes back.
At this point I have to believe there is a tank issue but the tank is 1400.00 and a used one is 700.00. Freightliners only option for us is to replace every single component in the system which comes out to like 18,000 which is more then the truck is worth. So instead of spending any more money and time with it I'm choosing to just get rid of the whole problem.

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