Well, the voltage is obviously coming from something on the lightgreen wire. You might want to check this wire to verify, it's the one going in and coming out of the brake switch on the pedal. The 89 diagram shows this wire going to the turnsignal switch and then makes it's way to the rear lights. It also shows the ABS and the cruise on this lightgreen wire. Your electric brake control will also be tied into the lightgreen wire.