2014 GL350 Connecting Prop Brake Controller


Connecting my 2014 MB GL350 w/factory tow package to Prodigy 2, electronic brake control (Prop Brake Controller).
Problem statement:
under dash connector (4 wire) for Electronic brake controller does see power associated with brake light. Appears to require setup in ECU(?) to enable circuit. MB factory tow package with 7 wire connector. Local MB Dealer Service Department wants to rewire.... Should be as simple as enabling towing circuit.