CM871 High DOC temp during regen

[JimT]

You mentioned that the doser injector was recently replaced. You may want to remove it from the exhaust elbow and double check that the gasket was put on correctly. I remember a pic Rawze shared of someone's doser where the gasket was misaligned and blocking most of the fuel spray. There is also a "thermal isolator" that shrinks over time. If it wasn't replaced with a new one when they did the doser then it could be affecting the performance. Likewise if the assembly wasn't properly torqued down there could be a bad seal letting air into the system. If there is an exhaust leak somewhere before the DOC then the fuel could be igniting prematurely. Just another reason to double check that doser.

Of course, you might want to double double check that the readings are coming from the correct location. If you have a thermal imaging camera then you can verify not only the correct locations getting hot, but also the approximate temp readings. Double check the wires and make sure everything is plugged in to the right locations. On my system the plugs only mated to the matching connector, but the temp sensor could have been screwed in to the wrong hole. --- I know you said you checked this already, but sometimes silly mistakes like this can be the easiest to miss.

Finally, the pictures above show what looks like orange coolant spots getting on to the DOC and partial clogging of the DPF (hence the off center soot buildup). DPF could have been a result of ash buildup so a cleaning might have corrected that. Staining on DOC could have been old. Just thought I'd throw that out there.