Is is necessary to have the relay #5 in the fuse panel on a 2004 Ford Expedition. Mine is missing.

I was working on trailer lights, and I am having some problems getting
consistent operation of my lights, especially the running lights.  I have
hooked the trailer up to other vehicles and the lights work, so I know the
problem is in the tow vehicle.  I cannot get any consistent lights except the
right turn signal.  I checked the wiring and it looks good.  I looked at the
fused that are supposed to go to the trailer package and noticed that relay 5
was missing.  It is supposed to handle the trailer lights as well as battery
recharge.  So just wondering if there was a reason it was missing and if it
could be the source of my problems.