Simple question I have headlights turn signals four way flashers and brake lights but I do not have taillights no blown fuses not very good with electrical heard the truck has had issues with a bad ground but I do not know how to find it

What is your question?

If it is a bad ground do I Start by looking under the hood or do I take the taillights out and check the ground there. When I last pulled my camper all of the lights also work but the taillights also did not work so now I am extremely stumped