Reoccurring DEF problem - Freightliner 2013 DD15

Approximately 2 weeks ago I purchased 2016 freightliner DD15 Cascadia with 498.000 miles.
Drove 3 days and got warning light come on with the SPN3251 FM0,SPN4364 18,
SPN3364 2 stopped immediately at the shop and they replaced a sensor and installed some awning kit since the #1 box had some buildup that was cleaned.
Drove 300 miles and check engine light come on with the SPN3251 FM0 ,towed it 20 miles to nearest shop.
Found out two fuel injectors bad and replaced it. Also replaced DPF filters with the new ones and NoX sensor. They did the regen and immediately this code SPN5246 FM0 come on and stay on.

 

5246 means that it is derated because of other codes. What are the other codes.

Could be injector, air leak in CAC piping, exhaust leak, bad one box, etc

What are the other codes?

 

The other codes are SPN3251FM0,
SPN4364 FM18,SPN3364 FM2

 

SPN 3251/FMI 0
Description
This Fault Code Sets when the Diesel Oxidation Catalyst (DOC) Inlet Pressure is 35 kPa (5 psi) greater than the Diesel Particulate Filter (DPF) Outlet Pressure for more than 10 Seconds

SPN 4364/FMI 18
Description
This Fault Code Sets When the Aftertreatment Control Module (ACM) Detects that the NOx Conversion is Lower than a Calibrated Threshold

SPN 3364/FMI 2
Description
Improper Diesel Exhaust Fluid (DEF) Quality

Could be:
-one of the sensors on the one box
-bad one box (or DOC or DPF)
-bad DEF doser or pump

Either way, shop needs to do some testing and diags with the laptop.

 

3251 - DOC may be face plugged. There is a diagnostic routine that runs a regen for about three hours to burn off what ever may be plugging it. If that doesn't work it maybe pushed back and may need a new one box.

 

I did my repairs at the MHC Kenvorth in
St Joseph,Missouri .
It was closest shop near me and technicians that work on the freightliner as well.
Unfortunately after replacing DPF filters and some wiring and Nox sensor 2 fuel injectors were bad. My bill was like 8.000$ and still codes comeback after the region.

 

Well that didn't last. Worked for about two months. 4364 FMI 18 happened about 20 times in last month. Only happens on hard pulls, but not every time.

 

Still have low NOx conversion codes daily, haven't taken truck in yet as May is our busiest month of the year.
The other weekend after reviewing the sensor logs on Diagnostic Link I noticed something odd. Every time I had a code, the EGR valve was recorded as being at about the 50% position. Odd as it should of been in any number of positions each time the low NOx code was set.
Saturday I set up Diagnostic Link to run as I went down the road. The ecu was commanding the EGR valve to move as expected, however the actual position of the EGR was always just over 50%. No matter what, it never moved. This should have set an EGR actuator code, but it never has. After 20 minutes I stopped the truck, left it and Diagnostic Link running.
I got out and moved the EGR actuator rod, Diagnostic Link confirmed that the EGR position was moving. I could make it go 0 - 100 % by hand, it just wouldn't do it on it's own.
So looks like I need an EGR actuator. Trucks going in this Friday.
EGR Commanded to 5%, but stays at 57%
EGR commanded to 43% but stays at 57% EGR position in blue graph, blue horizontal line is 57% . When it jumps down and up, that's when I moved it by hand.

 

Uncleal13 DL has a feature to activate egr valve's actuator at certain percent %. Actuate the actuator by DL and see its moving properly or not. Put 99% and see what is happening. Also activate at 50% and 10 %... when you activate at 50% the rod will be in the middle of travel path.
If actuator is not moving properly egr related code must be logged in addition of low nox.