Can't get ISX to high idle

I have a 2011 FL Cascadia with an CM871 ISX. I can't get the thing to go into high idle to save my life - tried turning the cruise on and off, tried using the accel/other buttons on the steering wheel, stepping on the clutch once, holding the throttle at a certain RPM and then pressing the buttons... nope, doesn't want to. Any other buttons to try or something that I might be missing? I'm headed up to Ohio and I know on Monday night/Tuesday its going to be cold enough to where the APU probably won't be able to keep the block warm enough, so I'll just idle overnight. Worst comes to worse I guess I could set up a stick or something on the throttle to get it up around 800 RPM or so, I just know that these ISX's HATE to be idled for long periods of time at a low RPM.

 

Yes, that would be me, lol.

I don't know if it has ever worked or not, not really sure about the history of the truck before I got it. It does have an APU though, so whoever owned it before me may have just figured they wouldn't need it.

For now I've made my own redneck high idle switch by wedging some lego plates between the pedal arm and the kick plate under the dash - depending on where I place them I can get it to idle anywhere between 800-1000 RPM. Good enough for these few nights where its cold enough I prefer not to shut the engine down and run the APU.

Next time I grab a load headed near home I'll stop by the Cummins shop and see if they can tell me what the deal is. If its a switch maybe I can talk them into getting me a wiring diagram so I can wire one up.