Yeah it's a little annoying. You can actually run the rear tires down to about 70 and the fronts down to about 60 and the lights won't trigger, but you can't go lower than that. Unloaded I wouldn't mind running mine at 65 all around but I don't really like looking at the light, so I run them a little higher - 65 up front and a little over 70 out back.
There is a fix over on the Cummins board, but you have to take it into the dealer. If you want to do that I'd print off the instructions from the very long thread discussing this matter (can't miss it), and then have the dealer reprogram the trigger levels. I need to get mine in for that ORC recall anyway so I'll probably have them reset the TPMS for me while I'm there.