This van doesn’t have tire pressure sensors.I "think" that your TPM tire pressure monitor receiver is in the SKREEM module also. I wonder if dropping the tire pressure will help diagnose that your SKREEM is bad?
Have you Googled "2006 Grand Caravan SKREEM" and studied all those threads?
Good Luck! Seems that you have done all the easy diagnostics. I hope you don't miss something simple.