Definately DEFINATELY...............it's the fuse box.
Do a search for the many items and replys I have made to describe and fix the "running lamp problems".
Replace the whole Power Distribution Module...............fuse box to you and I
and your problem WILL be solved!
There are corrosion problems seated deep within the fuse box, where the printed circuit board paths connect the FCM to the fuse box internally. These corroded paths, cause high resistance to ground, which the FCM uses to turn on the Park Lamp Relay. The FCMcannot switch on the Park Lamp Relay because of this high resistance.
There is a description of how to jumper the Park Lamp relay, to temporarily force the rear lights to work as AlexisRam
did, when he connected pin 85 to ground of the park lamp relay.
This emulates what the pathways embeded deep in the fuse box do.
My posts have a long and thourough "How to" on that, along with decriptions of the fault etc.
I replaced my fuse box 18mnths ago, and no more problems. Instant fix.
It really is a VERY frustrating fault that is easy to cure but costs $ in a new fuse box/PDM.
Hope this helps?