We're jacking the thread here I guess so sorry OP about that. The load seems to come from the exhaust brake. Just like you were warming the truck up with it, but it sounds a bit more aggressive. That might be from the RPM difference and/or adding fuel maybe. It doesn't kick off when the engine gets up to temperature though like the exhaust brake does. It's definitely not aggressive like how people have described when they activate a desoot with alfaOBD. And it doesn't do it just to maintain temp as you described, it will start it on a cold truck that has just idled for a few minutes while we wait for the bus. It's possible it might be preparing for the drive as you describe it. Whatever it is I have to say the strategy works well on this truck. We'll have had it for 4 years in early December and we've had no issues other than 1 exhaust sensor being replaced so far and a NOX sensor currently on order under warranty. Just a CEL, no limp mode. For a truck that never sees the inside of a garage even in -40 and is supposed to have very problematic emissions I'm not complaining. Yes at some point I will clean the intake thanks to the EGR just like we have to do to our gasser VW.I understand. My owners manual states that “If the engine is allowed to idle, under some conditions the idle speed may increase to 900RPM then return to normal idle speed. This is normal operation.”
A few years ago i went down the rabbit hole on how these systems work out of curiosity. Found some good information but it was not easy to source. Its kept from the driver and goes on in the background and most don’t care as long as they get from point A to point B.
I could be wrong but am relaying what i have read and how i understand it. My research has been confirmed by the CTS3. Maybe there is variation between years. But, my past 14 with the CTS2 and this 15 with CTS3 have never regenned at idle. The status goes from on to off once placed in park. I am glad they don’t regen in park. It would be a waste of time and fuel and how would a load be placed on the engine to generate enough heat? The needed load is higher and when a keep driving light pops you usually need to jump on the highway and/or try to stay above 45 mph for at least 45 minutes. The trucks at the dealer parked in the back running the desoot are idled WAY UP. They sound like they are about to blow with their hoods open and tons of generated heat out the pipe and from under the truck. Its a sight to see.
I cant imagine a Cummins regenning in park with kids running between the vehicles at a school. If yours does that be very careful.
I'll have a poke around once I have time after camping season is done. It would be interesting to see if it shows regen status active on there and if the VGT position changes compared to just activating the exhaust brake for warmup.