Reverse light help - 2003 GMC 3500 Duramax Dually 4x4 flatbed

[alabass]

Can't figure out what the problem is with my backup lights. I've checked all the fuses and have replaced the NS switch on the side of the transmission. Dome lights work, but reverse lights don't work on the headache rack or the rear of the bed. Anyone know which wire in the harness going to the bed is the one for the reverse lights? I have checked the bulbs and they are good also. TIA

[davester]

You've checked ALL the fuses, including the ones in the end of the dash by the driver's door.

[alabass]

Yes

[slj2008]

Check were the headach racks light are splice in , might have a broken wire , you can pull the taillight off , to see what color REV. wire is.