Regen issue

The way the ECM calculates the soot load is sorta goofy. It needs a consistent run on the highway to properly calculate soot load. Yes, the DPF differential pressure sensor could be faulty, but not likely. I have seen many get replaced and then 2 weeks later truck is back with same problem because that wasn't the issue. It is extremely rare for the sensor to jump around and read in error but still stay in range for the ECM and not log a code. Several things, first, since the DOC was replaced, it is probably still ok. Many times when the DOC is replaced, the DPF has been suffering from improper regens for a long time. Usually they become plugged beyond what cleaning can fix. Therefore there is good chance the DPF needs to be replaced also. I'll get back to that. The other thing for successful regens is cleaning or replacing the doser injector. This needs to be done yearly. Those pressure tubes need to be checked for plugging along with the ports inside the DPF. Ultimately, the engine needs to be tested to make sure it is healthy and not over producing soot and over whelming the system. This is what I do with trucks like yours...
Basic engine inspection to make sure everything is cool

Road test and record 0-60 full throttle full load snap shot. This will tell me if there are any fuel pressure issues, or boost issues, temp or exhaust back pressure issues.

Then I will do an Air Management Test. This runs the engine and tests the EGR valve, turbo waste gate and exhaust back pressure valve and engine throttle valve to make sure they are all working

Then I do a full forced regen and record that too. I will watch the temps and for any signs of weak or worn out after treatment such as lazy temp increase or visible smoke.

If the engine is healthy, then I focus on the after treatment. Usually the exhaust back pressure is too high, more than 5 psi. This will also cause low boost and more sooting. To confirm the engine is healthy, I will disconnect the exhaust and redo the 0-60 snap shot. If the engine makes full boost, its ok and problem is aftertreatment. With high exhaust back pressure, now you look at the DPF diff pressure. If it is more than 1.2 psi, DPF is plugged and needs to be removed and cleaned.

I suspect your DPF either was not properly cleaned, or is plugged beyond what cleaning can fix. When they clean a DPF, they will air flow test it before and after. All DPF have a pass or fail range. Even it is passes, it needs to pass with flying colours, not barely pass. Also, when they clean it, it should be baked for a full 12 hours at 1000 degrees, or whatever the machine does to properly bake out that soot.

 

Heavyd
i'm at my wit's end with my regen issues, 2012 maxforce, what stands out to me is when focing the regen the dozer opens to 14% then drops to zero, comes back on, drops again and the holds. what could be causing this. temps get up to 1200, soot levels drop to 35%, Additionally the truck will not take a parked regen. not dtc'sHELP

 

It does cycle like that at the beginning to "prime" the DOC, sorta like stoking a fire. So what is the actual problem? It won't started a parked regen? Is it asking for one? If you have software there to perform a forced regen, can you monitor "inhibitors" at all?

 

OK, yes i have software. yes truck is asking for parked regen, but will cut off 12min into it. when i hook up the laptop, i can monitor temps, they look good, 1200+. dozer opens from 12 to 23, 24%

 

OK, yes i have software. yes truck is asking for parked regen, but will cut off 12min into it. when i hook up the laptop, i can monitor temps, they look good, 1200+. dozer opens from 12 to 23, 24%

 

1200+ is too hot. Is it not setting any codes? Should settle around 950 to 1100 degrees.

 

I was at the dealership today for truck not wanting to regen (twice in a day) I was told a exhaust pressure valve needed replacement ($2900) and that may or may not fix my problem. I asked if the doser valve could be clogged, they hadn't checked it yet, they wanted to replace exhaust valve first to srr if that worked. With further inspection, they found fuel supply pipe to afi jad rubbed against block causing a hole ($85 for pipe, $730 to install). Does this sound reasonably quoted?

 

That fuel pipe is a bigger job. It goes behind the engine and there is no access unless you gut the interior and remove the rear engine cover. The line also wraps around the block on the left hand side and is just burred and hard to get to. Your exhaust back pressure valve is probably sticking and that is why they want to change it.