Brake lights work but not the taillights - Cars & Trucks

Since these are on separate circuits first check the front park lights and dash lights are going since these ARE on the same circuit. If not check the fuse. If that's ok, remove taillight bulbs and check they are not blown. You should be able to see the filaments between the prongs inside the bulbs. If they are ok with a test light check there is power going to lamp sockets with light switch on. If they are dual filament bulbs only one contact inside the light socket will have power going to it. The other contact is the brake light. You will need to identify it by getting someone to work the brake while you hold the test lamp on either contact with the light switch off then the other one is the taillight contact.