I have a 12v device on an automobile that draws about 1.5 Watts. I’m alittle concerned that the ground wire may be back feeding because the device is attached to the OBD port which has another source to ground. I want to put a Diode on the ground wire but I know very little about choosing the right Diode. What should I look for to handle the wattage rating of the device and also to handle the 12v?