Been doing a lot of miles recently and started to notice a grinding/dragging noise coming from underneath the rear of the car. So yesterday jacked the car and had a look, checked the wheel bearings, cv joints, brakes binding, rear diff/haldex and for oil leaks, but found nothing. I borrowed a mates code reader and the only fault that came up was 17947 Clutch pedal switch: implausible signal. Took the dash apart and got to the switch and everything looked ok.I removed it and tested it on the bench and it worked fine, so replaced it and tested in situ and it didn't work. After getting right into the foot well I could see the switch plunger was not depressing fully, making the contact. After it bit of modifying, adding a self tapping screw to the end of the plunger, it now works fine. Will get a new one this week just in case. Now after been out today, 70 mile round trip, the noise has disappeared, my question is this due to the switch working correctly and what does the switch actually do?