When I Hanniganized my 2009 GL1800 with TPMS I took the OEM TPMS out of service since the computer had to have the front and rear reporting to work. If wired correctly both TPMS lights simply don't light up and the INFO portion does not show.
I then installed a Trike TireGard and get a better tire pressure system than the OEM. I now can monitor real tire pressures in all three tires and get a flashing indicator if pressure is low. Just have to change the monitor AAA battery about one a month and the valve stem cap batteries about one a year.