code 3251.0

[davidjrawls]

2014 freightliner cascadia 125dc cm2250 isx Getting code 3251.0 Dpf Differential pressure Data valid but above normal operation range with red engine stop light on. truck had previously been running fine no codes or lights but fuel mileage seemed low. When I went to use truck about 3 weeks ago had an engine light upon startup so I pulled codes and it showed injector 6 code and aftertreatment pressure sensor code I cleared them and they didn't come back so went ahead using truck for couple days with no problems. I had ordered an imap sensor, egr differential pressure, and the exhaust backpressure sensor per the egr tune up videos I had watched on this forum. Was going to used truck today so decided to replace sensors before I did. Changed all three sensors and started truck everything seemed fine let it idle in farm yard about and hour while I was loading trailer. Took off down road and immediately when truck would start to pull and build boost then would loose power and sounded late a waste gate opening and dumping the boost. So I pulled over and looked at everything under hood and couldn't find anything obvious. So decided to ease on up the road to a better spot to pull off. Before I got to spot had engine light on. when I got there pulled codes and had a turbo actuator code and dpf code. cleared coded and the turbo code didn't return. but the 3251 code would not clear even with the engine off. then I noticed some black soot around the egr diff pressure sensor so I changed it back to the old one and also changed the back pressure sensor back to the old sensor as the new ones I got were not Cummins original ones like I thought I was ordering. still code was there and engine was in derate. I then removed the tubes from the dpf dif pressure sensor and tried to clear code with engine off and soon as light went out it came back on. So I unplugged the sensor and tried to clear code thinking it would give me a different code but still gave me same code that wouldn't clear. Also I don't have insite just a cheap code scanner.

[Rawze]

Your first mistake was not buying OEM sensors from an actual dealers$it. Half arssed purchases + tying to save a $$$ on critical components is absolutely the wrong attitude in trucking!!!. = half-arssed results.

next: If your getting DPF back-pressure and errors the you need to pull the DPF and DOC, take pics of their faces .. post them on here for review of what has built up on them. Then take them to a certified stelaers$it and have them baked, de-ashed, and flow tested. Then do a maintenance reset in insite so that the ecm knows you did this too.

Replace the DPF diff pressure sensor as well, and clean out its cross-tubes, replace any worn out rubber joints, etc. so that it can read correctly once the new cans are back on too.

[davidjrawls]

I wasn't trying to save money was trying to get oem parts they just didn't come in that way. I just cant figure out why the code will not clear. There shouldn't be a difference in pressure if the engine isn't running? If you think i need to check them I will. But it was running fine and no regin or engine lights ect. It only idled about an hour today after i changed the sensors and then went about five miles.

[Bengy88]

That code won’t clear without a successful regen with good readings across the board. I had an isl come in last week with this code accompanied by a 1922 and 1921. Dpf and doc cleaned and tested, tubes cleaned, and new differential pressure sensor before I tried anything…. This should be a rule of thumb.

After that I performed a reset then a regen. Regen was near perfect other than taking 1.5 hours and temps taking too long to reach specifications but code still went away, till I drove it….. you know that egr tune up thing we keep talking about? Had to do one for everything to work as it should. Do yourself a favor and start where Rawze said and clean your egr on top of it

[davidjrawls]

Attached are the pictures of outlet side of doc and inlet of the dpf. Can’t get a picture of the doc inlet

[Bengy88]

What does the outlet of your dpf look like?

[davidjrawls]

I didn’t get a picture but it’s clean as can be can’t even get ur hands dirty on it.

[Rawze]

that actually looks fairly decent. Nice fine soot and no signs of coolant or oil intrusiuon there.

Without a pic of the face of the DOC though.. one cannot be sure. Does the inlet of the DOC look as nice?...

If you removed the DPF to get cleaned .. then you also, always need to do the DOC element too. It clogs up and gets face plugged just as much.

BOTH have to be cleaned... and that pic shows that they are due... especially that DOC element.

Also, I think most people have this false assumption that if they do a 'forced regen' or 'parked regen' that the regen system will clean the DPF out effectively .. but this is absolutely NOT the case.

The regen system on the vehicle is only about 5-10% effective in cleaning those elements .. even if you were to perform it several times. Once the system starts complaining that it wants a parked regen .. its time to pull the (DOC and DPF both) cans off and have them baked, de-ashed, and then flow tested on proper machinery. Otherwise simply doing those parked regens on the truck is nothing but a short term band-aide that will only get you a few weeks at best before it complains all over again... eventually putting you on the side of the road.

Pulling the cans every couple years and having them fully baked, combined with thorough, yearly EGR tune-up work so that the engine does not produce the soot to begin with.. and you can bring one back to its "new-like' state where it will not act up for a couple years again... unless there is something wrong with the engine. Engine problems like allowing oil or coolant to get into the exhaust, bad or leaky injectors and other things that might cause higher than normal soot levels, etc. needs to be prevented.