P244A Diesel Particilate Filter Differential Pressure too low

[Wayne M.]

The earlier trucks used to throw the code sometimes at high altitudes.

I would buy that.

 

[firemansdiesel]

I imagine it could be one of three things. Soot in tailpipe that means cracked/bad DPF, bad sensor where the differential tubes attach too, or exhaust leak. Also with all the electronics on these newer trucks. It could be a phantom code that can be cleared and not come back without any real issue.

 

[Wayne M.]

I'm sticking with sag. The change in elevation changed the values the diff sensor sees and has been seeing. If there's no sign of a breach- soot out the tail, then I wager that everything is fine.

 

[TRAMPLINEMAN]

Maybe, but the elevation I'm at in WI is 1,195 and in MN is 1,371. That's not that great a difference and I've made this same trip probably 100 times before.

 

[EDankievitch]

I just threw this code (P244A Diesel Particulate Filter Differential pressure too low) on a trip from Ny to Va. Every time I'd change speed or stopI'd get a message and a CEL lamp on the dash. Found Star Motors in Suffolk Va. nice bunch were able to get me in quick. Any way their TEC found "Moisture inside the lines going to the sensor." They replaced the sensor and all is good. Now my question is.... How does Moisture get into the sensor lines? These lines are on both the in and the out sides of the DPF. It's my understanding that the DPF is dry exhaust going through it. It's in front of the SRC. So how did moisture get into the sensor??? The TEC said that they have seen this problem a few times before. Any thoughts ? Should I keep this sensor part number 1 68085750AB on the shelf ?

 

[MichaelOverfield]

Elevation here is 1371'. When I started the truck this morning, the engine light was on. I moved the truck about 200' and shut it off. Started it back up, engine light is off. I don't know?!

It might have been an issue that cleared. I had mine throw a code for DPF filter efficiency below threshold.. I'm thinking it might be time for DPF to fall off.. but it also cleared, and after a long highway drive, towing the truck completed a Regen, and it seems to have been fine ever since. It could have been an issue that cleared up on its own, or it can be a sign of early failure. Look for soot inside the tailpipe after you've driven for awhile, if you never see any soot, it's probably nothing, if soot starts to show up, it's sign of a damaged DPF. I have one diesel that had an early DPF failure in the first week that had to be replaced, it was diagnosed by soot from the tailpipe.

 

[MichaelOverfield]

.... How does Moisture get into the sensor lines? These lines are on both the in and the out sides of the DPF. It's my understanding that the DPF is dry exhaust going through it. It's in front of the SRC. So how did moisture get into the sensor??? The TEC said that they have seen this problem a few times before. Any thoughts ? Should I keep this sensor part number 1 68085750AB on the shelf ?

Normal hydrocarbon based fuel combustion produces ideally CO2 and H20 as exhaust... all other things that come out are the reason for all the emissions controls. There is ALWAYS water vapor in the exhaust. When you do many short drives where the temperatures never get very high in the entire exhaust, the water vapor condenses in the cold exhaust pipes, and is sometimes literally seen dripping out the tailpipe.. that is where the water comes from.

 

[Newsa]

Normal hydrocarbon based fuel combustion produces ideally CO2 and H20 as exhaust... all other things that come out are the reason for all the emissions controls. There is ALWAYS water vapor in the exhaust. When you do many short drives where the temperatures never get very high in the entire exhaust, the water vapor condenses in the cold exhaust pipes, and is sometimes literally seen dripping out the tailpipe.. that is where the water comes from.

Yeah. Quite a bit of water vapor is produced. The sensors should be designed not to foul in water.

 

[EDankievitch]

This truck has been doing roughly 650 miles a week all summer so short trips are not the issue. I was 275 miles into a 451 mile trip down to Va Beach when it acted up started throwing the CEL and giving me the Exhaust system needs service message every time I'd step on the break. It would clear when I was moving for a while but would return as soon as I hit the break. Al that water vapor you see on these trucks is from the DEF and that is down stream of the DPF. Have the fuse blow like I had on the DEF pump and you'll see a huge difference in the amount of water vapor coming out the stack. That pressure deferential should be able to handle the normal amount of vapor made. My unit according to the service TEC had quite a bit in it. I'm just shy of 80k miles on this truck, I guess I'll have to remove the sensor hoses and blow them out from time to time????

 

[MichaelOverfield]

Odd, my truck has no DEF, but plenty of water from the exhaust. My gasoline powered vehicles get it as well. My 2 Diesel Chevy Cruzes have DEF, but use very little, not enough to account for the amount of water vapor from the tail pipe. Combustion produces most of the water vapor. DEF might be a significant factor if you have some type of malfunction, but it's not a factor across the DPF in any case.