2008 Titan Backup lites

I am having trouble with the backup lights on my 2008 Nissan Titan Pickup. I have checked all the fuses I can find. It does have a trailer plug that was added through the place provided on the truck. Since my trailer has no running lights I was thinking that the two problems may be connected. Is there any fuses besides the one under the hood and the one inside the cab? I had the trailer plug added at a shop that specializes in such installation. It has been on for 4 years and working so, I can only think it is fuses. Can you help me?

Fuse 28/10 amp and fuse 51/10 amp supply power to the backup lamp relay. The relay is contolled by the transmission control module. So either the backup light relay has a bad contact where it’s not turning the backup lights, or the transmission control module is failing to close the contacts in the backup light relay.

Tester

The first thing, which wouldn’t take much time, if you have the expertise, remove the bulbs, and probe using a dvm at the backup lights to prove/disprove whether there is 12 volts at the associated light socket when backing up. I expect tho this will prove to be some switch contact associated with the tranny that is faulty or needs adjustement. Sometimes the engine and xmission will move a bit in their mounts as the car ages, more likely to happen if the car is driven aggressively or over bumpy roads, and all this causes the motor and xmission to move around. If so, no worries, it is probably just a minor adjustment.

I am having trouble reaching the “tranny” I have pulled the truck up on ramps I have for changing the oil. But the point where I think the connection is located is recessed behind so much that there must be some way to reach it that I don’t understand. Please go in to a little more detail on how to reach the point that needs adjustment. Thanks so much for your information. I appreciate it greatly.