Because the brake switch is always powered, you could check the 2 wires at the switch and determine if the switch comes on when the brake pedal is lightly touched. Or have someone watch to see if the lights at the rear come one.

To erase codes, read the codes until you are back to the first one that came up, then hold the button down for 7 seconds. When the red light comes on again, hold for another 7 seconds. That should get you to 1-1-1. If the codes still reappear, then the fault is still there and must be fixed.

Klaus

--
Proud owner of a 220S. If I had more room, I would have more Volvos.