Ford F-150 - 1997-2003 :: Reverse Lights Not Working

I have an automatic 5.4L (L code) 2000 Ford F-150 and I am having problems with the reverse lights not working when I place the transmission in reverse. Fuse #5 in the passenger compartment fuse panel is good and both reverse lamps are good as well. I have also metered the LB/PK input wire at DTR sensor and it is reading 12 volts when the ignition is in the on position. I have also the metered the BK/PK wire output wire at the DTR and this wire also reads 12 volts when I place the transmission in reverse. I have checked continuity from the BK/PK wire at DTR to the BK/PK wire at the reverse lamp socket and I do not have continuity. I then ran a fused jumper wire from the BK/PK wire directly to the BK/PK wire at the reverse lamp socket and the lamps will light up when I place the transmission in reverse and will also turn off when the transmission is placed back in park. So it seems that the DTR is not defective. I'm not sure what else to check. Obviously the BK/PK circuit is open at some point between the DTR and the reverse lamp socket, but I'm wondering if there is something else that I need to check. The vehicle is also equipped with a factory trailer tow package