08 ISX won't regen

I've got 2 trucks with Cummings engine with similar problems. One the filter needed to be replaced, the other one the injectors where bad.

 

the differential pressure sensor is one of the components that will tell the computer it needs a regen. The computer will sense that there is to much pressure going into the dpf as opposed to the outlet of the dpf. Makes sure the face of the dpf is cleaned and check the parameters of the dpf sensor. If that comes back clear then take the 7th injector out of the exhaust pipe just after the turbo and make sure it is clean. They love to get clogged up.

 

Is the high exhaust temperature warning light coming on? At this point you don't know if it is even dosing any fuel. You don't know if it is making any heat or not. Any smoke during the regen? Sorta need Insite connected to see what is happening.

 

Intake manifold air pressure sensor / about $50
Delta-p differntial pressure sensor (intake manifold to venturi pipe) / about $150
Clean those cross-over tubes between intake manifold and "venturi" pipe, i use carb n chocke cleaner

Maybe look into changing your exhaust back pressure sensor, those have a 500k mile or so life span / about $125

These sensors feed the data to your computer !!! They get carbon packed and dont read right...

Theres another sensor too, on the dpf can itself, dpf differential pressure sensor its about $150

Change all of these if you can at once to make sure your on a level playing field. All of these sensors can be changed with simple sockets and wrenches

 

The exhaust has to be 525 degree or hotter in order to the system to allow fuel dosing to take place. Not seeing the high exhaust temp light is a for sure indication no fuel is getting dosed. The back pressure and engine load is created by the turbo to make that hotter exhaust temps up to 525 degrees. So this needs to be looked at next.

 

If you don't have a laptop with Insite, trying to solve this issue becomes way more difficult.
If you don't have one, get yourself an inexpensive laptop with Windows 7. Used is fine, format the hard drive to wipe it clean. This is now a tool NOT a toy. Don't ever connect it to the internet! DO NOT risk putting a virus in your ECM.
Go onto eBay and buy yourself a Chinese knockoff Inline 5 adapter, they're not expensive and they're invaluable to an O/O.
If you have one, or have access to one, connect the ECM to Insite and post the regen history. This will show the results of the last 10 regens (or attempted). This info is the first step.
The next step involves a good day of getting filthy. Buy at least a case of carb cleaner (not brake cleaner, the chemicals in brake cleaner mess up sensors!) and start removing the EGR system components (exhaust gas pressure sensor supply tube, crossover bellows pipe, EGR valve, Venturi mix pipe, intake manifold, etc. DO NOT clean inside the head, don't risk knocking a piece of carbon down into the cylinders! If your real adventurous, undo the EGR cooler inlet from the exhaust manifold and cover/plug the manifold from contamination and use EGR cooler cleaner to clean out the capillary tubes of the cooler while the crossover is off so it can escape safely) and clean the soot out of all of this. Replace; IMAP sensor, EGR Delta P sensor, Exhaust Gas Pressure sensor, DPF Differential Pressure sensor, and if your doser is more than 2-3yrs old replace it as well.

An '08 truck most likely has some miles on it. Cleaning your DPF is good, but the DPF is NOT what causes the diesel to ignite, the DOC in front of the DPF has precious metals that ignite the diesel via reaction to burn the ash the DPF has collected out of it. The metals in the DOC have a lifespan and if it's never been changed, it's probably due.
These after treatment systems have a lot of components and sensors that get soot packed and need to be maintained by regular cleaning and replacing. This should be done every 250k miles or so to keep the CEL's at bay...
Good luck.

 

I don't know how any of these guys expect to fix anything without the proper tools. You are really hand cuffed without it.