working principles of Electronic Throttle Body
Looks like some form of capacitive or inductive rotary encoder to me. 

Presumably some common signal is coupled into that six segment yoke through the four turn outer coil on the PCB which then couples back to the radial segments on the PCB via the spokes on the wheel.

Hard to tell if it's capacitive or inductive though without seeing what is on the other side of the board and maybe a scope trace if two, but my $1 is on capacitive. 

Either way, I'd guess those four pins pass quadrature position information though the S1 and S2 pins.