good tip to use a bulb instead of a meter so it isn't fooled by voltages with no amperage which can show up and confuse someone with a DMM.


maybe this seems like a radical change ,,

all you really would need it to use a brake fluid pressure sensor from an older car and then just pick up power from an unused fuse or add one,

run that to the brake lights and then to ground. simple! 1 wire running two bulbs.

That would eliminate a whole lot of unnecessary complication.

Volvo prided themselves on making good safe cars but I think they got led astray with this section of the wiring. It's way more complex than needed and that over complexity in itself caused a system that was prone to failures and caused owners much grief in trying to wrap their heads around it all.