To the original poster.
That light usually only comes on when the brake system pressure is out of balance and the out of balance pressure causes the valve in the distribution block to shift to one side causing the light to come on.
For example, if something is wrong with one end (front or back brakes) it throws the pressure balance off and causes the little valve to shift one way or the other off center.
This makes the warning light come on.
You did say the brake pressure felt soft.
