I have kenwood excelon ddx 7015 unit powers up but says a cord is not pluged in. Wanted to know if this unit has a internal or external brain box and if it has an external brainbox how do i find one
I have a DDX7015, and can tell you that the unit is completely self-contained. You can get a kds-p901 external 5.1 processing unit that deactivates the on-board processing brain; the 901 connects via fiber optic.
It sounds like your constant power (yellow) is not energizing. You can test that pretty easy - you should be able to hit the eject button with the car turned off, and the faceplate should lower.
Try pulling the unit out and checking the in-line fuses and the wires - you may find that the wires got crushed during installation. To test functionality, you can try twisting both red and yellow together, and connecting it directly to the battery. You may find that your 'constant power' in your dash is unable to supply the current this head unit needs (7-10A, if I remember correctly). If that's the case, you may need to run a dedicated wire out to the battery for the yellow. Make sure you put a fuse close to the battery. The fuse is not to protect the head unit, but to keep the wire from burning up in the event it gets shorted, so the fuse can be 20A or so (the head unit should have its own fuse).
I hope your head unit comes to life - I've had 6 years of great service from mine, and it plays mp3s and wmas directly off of a data DVD, and works great with the KNA-DV4100 navigation system.