Running lights rear on 2006 Grand Jeep Cherokee Laredo do not work even with replacement. Brake, Signal and backup work.
check number 7 micro relay in the Under hood Fuses (Integrated Power Module)
Jeep Grand Cherokee (2005 - 2006) – fuse box diagram - Auto Genius
Also check the ground and power at the bulb socket.
Are you sure you don’t just have your daytime running lights on? They don’t turn on the tail lights.