Necessary Fuse?

I'm redoing an alarm install in my Nissan that was poorly done at this place called Audio Express.  It was so bad that it would actually make the car easier to steal.  Anyways, I noticed after removing the DEI Rattler 300 that on the door lock harness with the purple & PURPLE / blk wires that are connected and go to ground, that there is a 15A fuse in line w/ these wires.  Is this necessary since the power wire already has an inline fuse?

Yes, this could be there so if the system has problems with the door locks just that fuse may blow and not the main fuse powering the whole system. Besides it never hurts to fuse!

The 15-amp fuse on those purple wires you see is part of a separate module....the 451M as you'll see. The 451M is just basically two ordinary relays, prewired for convenience. The fusehold is prewired to it as well. That relay module is for use on all manner of different doorlock systems, and some of them switch high-current positve power through the relays. Your particular system only works on low-current negative.........the factory wire is grounded to perform one function (either lock or unlock).....and the wire is interrupted to perform the other. For your particular application, the fuse is not necessary, but it would accomplish no good to remove it, either.