Well, the simple thing would be the fuse #7 is corroded or cracked in the middle (as they all will). You will measure 12V on the right side, at the fuse holder clip, but it will be coming from the cruise control, or if the fuse was corroded, it will be just low current passed through the crud. The point of asking if the voltage remained when the pedal was down, is that voltage would now be connected to the load.

So continue your troubleshooting where you left off, backing up from the blue/red on the sensor, through the pedal switch, winding up at fuse #7. Do it with the pedal down to ensure the load is given to the fused circuit. A meter will see the slightest current, such as the input circuit of the cruise controller, or leakage through a cruddy fuse. A real test light is better for this kind of chasing. This diagram does not show the cruise control tap at the blue/red between the switch and the sensor. Sorry it is the Europe version, not showing the high mounted brake light either.



--
Art Benstein near Baltimore

Friends don't let friends drive w/o brake lights. :)