If we put in the sockets four 7-segments LED common cathode LCD display devices, we should connect the pin 33 of the board (the common pin) to the Arduino GND signal. At this point, all works fine ...

This is what it looks like in action: My model uses the car's OBD-II port to connect to an Arduino microcontroller, which is programmed to display the car's speed on a 7-segment display.