Def Quality issue Paccar MX13 (2024)

I’m working on a 2016 Peterbuilt 579. The driver went to go on a night run and the truck is full derate, Def light flashing. Codes say def Quality and fuel filter restriction. The Def quality harness has not been connected and is capped. I’m assuming because it’s a different Def pump but I maybe wrong. But so far I’ve changed fuel filters, Def filter, siphoned as mischief Def from the tank as I could and put all new def in, even tried testing a new Nox sensor which brought up a new message saying repair SCR and when I put the old one back in, that message went away. I pulled the doser off and checked and it meters fine also it wasn’t caked like Ive seen from people’s videos but that’s not saying it’s not working properly. Also in the exhaust after the doser I noticed the connections have the crystallized def, Does that mean its more then likely the doser? Anyone have any ideas of what I can look into next or does the doser possibly cause the def quality problem.

well you have to reset derate and make sure def is not frozen, than the truck has to drive for 50 miles or so some truck have def quality sensor mounted in the def tank that might be you issue.

What are you using for diagnostic tool? You will likley not get derate to clear without Davie, factory tool. You must disable the derate and road test for the monitors to run and complete. Bad Nox sensors are common. DEF sensor does not measure DEF quality until 2017 EPA.

EPA 13 uses NoX sensors to calculate NOX quality based on conversion efficiency.

That code sucks to trouble shoot. I have found doser causes the problem most of the time. Check spray pattern and amount should be around 80 ml and check for leakage. Then disable derate with davie and road test usually clears in about 20 minutes of highway driving.

I have diesel laptops. They informed me that there was software that they have separate that’s 300 just to send me the computer to clear it. I’m about to replace the doser which is not working properly. So the only way to clear it is a dealer set up?

A company around me says they have the software that will clear and it’s the snap on diagnostic tool. They haven’t been able to get it to clear yet so is it because it’s not the right equipment or is it possible that the replacements just didn’t fix it to be able to clear

The only 2 pieces of diagnostic equipment that can CLEAR (not read) codes are (1) Paccar Davie (2) OTR specific plug in tool for Paccar.

I have had a driver take a truck and it cleared by itself but you risk derate without davie to disable derate.

Depends, I have had it go both ways.

If its speed limited you have no choice but to disable with Davie.

New def sensor, nox sensor, ran a full regen and it’s at normal for soot but still won’t clear. The owner don’t like it but I told him it needed to go to a dealer to get it cleared cuz the def isn’t frozen or anything and it’s still giving the def light. I hate paccar