Somehow I cannot locate ED-E therefore I cannot dismiss him as a companion when I try to start the Heart's DLC. ED-E shows a marker on my map ( actually in the area of vault 22) but for the love of all thats holy I cannot locate him either within the vault or outside the vault. What is weird is that it appears he is with me but not visible because I am still receiving his perks and Jed still recognizes that I have a companion with me. So is my only option to start a new game from scratch and work my way to the Northern Passage or hope like heck I have a save file that either shows ED-E or one before I had a companion??? Any suggestions would be appreciated. Thanks in advance!

If you're on Core mode, he has most likely exploded. If he takes enough damage, and then even more when unconscious, he will explode like any other robot, but still be your companion. I still haven't gotten him back, and the only way I got rid of him was by starting Dead Money.

If you're playing hardcoe, I'm not sure where he could be.