Failed after treatment test Cummins ISX

First I need to state that I'm self taught when it comes to aftertreatment problems. Looking at your status messages check for exhaust leaks before the DPF back to the exhaust manifold gaskets. Looking at the regen history 7,8,9, and 10 look normal. 1 and 6 are close and 2,3,4,and 5 look cold. The DPF outlet temps should be a little hotter than the inlet temps. With differential pressures it seems any number above 2.2 or 2.4 I start getting codes. Hope this helps.

 

Like mentioned, the last few regens are too cold to start fuel dosing. The inlet temps to the DOC must be hot enough to start this sequence. The primary part responsible for creating that heat is the turbo by closing off the vanes to cause high exhaust back pressure. With the vanes not closing enough, the exhaust back pressure is too low and no heat is generated to cause your low regen temps the low back pressure message from your regen test. Faulty sensors can also cause this, such as exhaust back pressure sensor and intake manifold pressure and egr differential pressure sensors. Removing and cleaning these sensors or replacing them is sometimes the corrective action to take. Stuck open EGR valve can also be the cause of low regen temps and low back pressure. You can monitor for a partially stuck open EGR valve by watching the EGR differential pressure reading during a regen. During a regen, the EGR is commanded fully closed, so EGR diff pressure should be 0.0. If you see 0.2 or higher, it means the valve is not fully closed. Some people get lucky with removing and cleaning sensors, others have to replace the turbo to get this fixed. So start with the cheaper options first.