Not knowing, if or if not the pads are worn down to the sensor, I would suggest a close inspection of the senor wire. As nelbur already pointed out, in some cases the insulation can wear and close the circuit by touching other conductive materials. This can happen if the wire isn't routed correctly and may touch moving parts during every day driving until it is blank wire..

I had an intermittant flash of my warning indicator and it turned out to be a blank wire!

__________________
Mostly, I don't know notin, I just know where to look.
I am looking back, to over 30 years in Electronics Design.
Electrons don't care if they move in a car, computer or relay!

95 W124 E320 M104.992 - Because, I love to repair, naaaah!
Over 221,000 Miles
Cheers,
Norbert