Dodge turn signal problem

[49merc]

I have a 2004 Dodge p/u with the tow package. My left turn signal to the trailer (which is separate from the truck signal) has quit working. I have no output to the pin at the trailer plug. I thought it was the trailer but dealer plugged his test box into the truck and showed no output. He said I probably had a blown fuse. I checked the fuses and found the trailer running lights fuse was blown and replaced it. The odd thing is the running lights worked just fine and both left and right fuses checked ok. Does anybody have any ideas before I run it into the Dodge shop in a week.
Thanks
Bob

Update on turn signal problem. Turned out to be the PDC module. Of course Dodge had them on back order so it took awhile to get it repaired. Glad I had service policy as it would have been a rather expensive repair.

[Charlie]

I have two fuse boxes on my Ford. One is under the dash and the other is under the hood. The one under the hood fuses the trailer lights separately. I had the same problem, lights on the TV but no brake/turn light on the left side of the trailer and found a blown fuse under the hood.