Hello all. I need some help. I just purchased a used oem trailer hitch and harness. I installed it and found that the lights for my trailer were not working. I researched it and found that I needed to install some fuses in the fuse block in the engine compartment. I did this. Still no lights.I checked the wiring connections. OK. I thought this was a plug n play system. I guess not. Do I need additional parts? Thanks.