Something ain't right. That’s how I do it on both of mine. Doesn’t matter if the trailer is already hooked up or not. Step 1 for me is to turn off the park distance control and then step 2 is to use the top button for the DIC controls on the dash to clear the message and go back to the odometer or whatever other thing I want to monitor. Wonder if the BT Dieselworks stuff is interfering for you.That button is already lit and does nothing when I press it. I probably should've done that before hooking up the trailer, lol
Edit: saw you got it sorted. I assumed you were already pressing the DIC button. Lol.