ABS light

Its either an abs sensor, or what is commonly referred to as the brain which controls the abs system on the tractor. It is usually located under the 5th wheel, and its expensive! Around $1600

 

Piece of black tape, they don't call it A "BS" light for nothing,,,

 

Volvo has this everlasting problem - ABS and TCS dashboard lights on. You could throw tons of money at it but sooner or later these dashboard lights will always come back on.

 

Sensor, wires or brain, basically that is all there is. Make sure all sensors are pushed all the way in. Clearance is very small.