It goes from the P pickup out to the side of the body. Look at the picture and you can see it on the left side of the picture. When the bass is indoors, it's rarely able to be seen. I had to point it out to my wife and even then she said she thought it was just part of the wood grain pattern.
I KNEW that bass was familiar. That one originally came to my local dealer here. I just about bought it, for a mildly discounted price due to the crack, but I really wanted a 5 string instead. They sent it back to the Spector distributor after I decided not to buy it. I agree--it is hard to see unless the light hits it just right. But that is one hell of a nice playing and sounding bass. Bet it kills with the EMG preamp in it.
I wasn't impressed with the Tonepump in mine either. I opted for the Aguilar OBP-3 at 18v in my five string, but I was seriously considering ordering an EMG pre at first.