Amazon: Metra 70-1783 Radio Wiring Harness for Smart Dec 15, 2016Installed a Pioneer head unit in a 2012 Smart Fortwo Passion and used this wiring harness. Harness is great except two wires need to be moved which took about 30 seconds. Slide a paperclip or small eyeglass screwdriver along the top of the wire from the front to release the wire and slide it in the correct slot and you're good to go.3.6/5(25)Price: $8 SMART Car Radio Stereo Audio Wiring Diagram Autoradio SMART Car Radio Stereo Audio Wiring Diagram Autoradio connector wire installation schematic schema esquema de conexiones stecker konektor connecteur cable shema car stereo harness wire speaker pinout connectors power how to install. SMART Car radio wiring diagrams. Car radio wire diagram stereo wiring diagram gm radio wiring diagram.