Is there a fuse or relay for the running lights?

Both running lights on the back of my 2005 Mercedes CLK320 are in-op. I've changed the bulbs twice to see if it would fix it and it has not. Also had a gentelman at O'Reilly's take a look at it. it is definitely not the bulbs. we tried to see if it was the fuse, but the fuse chart says "electronic," so i'm thinking there's no fuse for this particular operation. were we interpreting the fuse chart incorrectly or is there a possibly a relay or a module somewhere that needs to be replaced or am i totally in left field somewhere? Thanks