hairpin speed sensor broken

[Nana]

just had my 172 mk2 serviced and the mechanic said i have got a problem with my hairpin speed sensor (a part of the traction control i think?). what is it, where is it, do i need it?

 

[montana]

shouldnt you have asked him??

 

[viceroy]

is that the thing which tells the speedo how fast youre going?