CEL codes U144F and p24c7 on 2014 GLK250. Any clues?
 

Hi. I am working on a 2014 GLK250 diesel and I keep getting these two codes and I've searched everywhere with no clue on what they mean. They are U144F and P24C7. Can anyone tell me what is going on? Car had some other codes before and I replaced the oxygen sensor and two temp sensors in the DPF and now these are the only two codes left.

Any help will be greatly appreciated.

U144F - "Minimum fuel level REACHED" is the response. Occurs when you've been running the tank almost empty numerous times.

P24C7 is something to do with DPF temp sensor issue, maybe wiring or an implausible signal.

How is the DPF itself? Do you have sooty exhaust inside the tailpipe? Can you run a DPF regen?

Here is the deal, I cleared the codes and the U144F and P24C7 codes came back after like 30 miles of driving but the fuel tank was 1/4 full...is that considered too low?

As for the DPF, I haven't checked for soot or perform a regen (my SDS won't connect to this particular model for some reason), I can only use my regular scanner. I just changed two of the temp sensors on the DPF based on some other codes it was giving before but these two came back. I am wonder if the issue may be the differential pressure sensor which sometimes is referred to a temperature sensor for some reason. I feel like swapping that out just to see.

Thanks for your help, any more info you have will be appreciated.

I can't say with any certainty that running it on 1/4 tank would cause it, but why not fill it up and take it for a longer highway blast? Maybe that will help reset the SCR system.

You could replace the differential pressure sensor as well and see if that fixes it. No issues with the current NOx sensors?

i would start with a scanner that can read the correct codes, 1) Carly for mercedes, or 2) icarsoft mb2

I would agree; a feature rich MB-specific scan tool is a worthwhile investment if you plan on keeping the car and maintaining it yourself. The SCR system on these Bluetecs is particularly complex and a huge pain in the a$$ without proper tech and tools.

i recently had an issue where the generic scanner was giving me a nox sensor code, really it was “the output from the fuel pump implausible” which led me to investigate my fuel filter change that was recently completed. Wouldn’t have known that without the icarsoft mb2 that was 200$ On amazon in canada and I have for life which works for ALL Mercedes and has free firmware updates....

i was was also able to clear all the code and reset the stupid start countdown with it.

Running great for 10k now...

Interesting tidbit since I'm planning on doing my first fuel filter change (myself) in the next weeks. What (if anything) ended up being the problem and solution there? I currently use Lemur's BlueDriver tool, it works pretty great for what it is.

Its easy to change, but two things, once you change it let it fill for like 2+ min with key to ACC mode before starting the car. Second do not reuse the clips. I did not have a perfect seal and a bit of fuel was escaping which causeed my fuel flow implausible code. I ended up buying new fuel line hose clips (that screw tighten) instead of using the Mercedes ones that require a special tool.

I have a Mercedes SDS Compact 4, I just need to update it.

Anyways, tomorrow I'll play with it some more and we'll figure it out. Thanks.

So I changed the DPF pressure sensor and light hasn't come back on in the 50 miles I put on it. We'll see as the miles rack up.

I checked the tail pipe for soot and it had a decent amount, thought it's not BLACK. But if I run a white cloth it'll come out dirty. Does this mean the DPF is crapping out?

I have an updated SDS coming my way so I'll try to force a couple of regens on it if it comes back.

@GT-ER
Sounds like you may have fixed the issue. If all the sensors are working right, the DPF should be made to regen at the proper time as long as you're driving it enough. I know mine does a regen every 300-500 miles, and I can tell from a slight increase in idle RPM as well as a different smell coming from under the vehicle when at a stop. So far, in 93k miles (knock on wood), no exhaust issues have appeared. I've only had to top off DEF fluid several times. By the way, I'd now make sure the DEF tank is full too. I've also checked my tailpipes and I have no soot. Looks like the DPF is going strong and I'd like to keep it that way. It may be that with the faulty sensors, the DPF wasn't being scrubbed clean and some soot made it out. You can try again in several hundred miles to see how the new sensors are working. There are also DPF cleaning fluids you can try, Lubro-Moly makes a couple.

@C300fan
Thanks for the heads-up on the fuel lines clips. I'll make sure to have some handy when I do the job.

Well, CEL came back on but the customer will be away for a few weeks so I can't check it till then. I at least got my SDS updated to 2019 version so I should have no problem reading the right codes now. I'll update this when I get to it, but I suspect the DPF is just dead.

Bummer; keep us posted on what you find.