Had a red tagged printer that would not sense the filament on sensor 2. The sensors had been swapped and another assembly was installed as well to eliminate the sensors being the issue.
Was able to find with a multi-meter that DAC1 connected to the filament sensor 2 is shorted to ground on the Archim board. With the board removed from the printer and all connections unplugged DAC1 is still shorted to ground. Board determined to be bad, installed new board and issue no longer present.