I have bought some Gadgetman parking sensors off eBay (I know cheapskate) The sensors are fitted in the bumper. Control box is connected to reversing light feed and earth. This model has a separate display which must work by some wireless means. It is connected to the cigarette lighter/power socket and (should) show distance and emit a beep. When the display is connected it lights up and beeps and then immediately goes out. I have tried dispensing with the power connector and wiring it direct to the live and earth, via fused link and it does the same. In my ForFour I had to buy a separate Canbus bypass relay for them to work properly. Has anyone got any idea please?