There is no sensor. The wires are set into the pads themselves. When the pads are new the wires are intact and the circuit is complete. When they wear down to a point the disc will break the wires and interrupt the circuit, and the warning lamp will come on.
Volkswagen Sharan 1.9 tdi 90bhp 2002 - brake pad wear sensor - elekie&a/c doctor
If the new pads had new sensor wires fitted,and the light is still on,then it is likely there is a break in the wiring to the connector plug where it runs down the suspension strut.
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