I was looking over schematics for another "project", and saw that the LLY ECM has a circuit labeled "Fuel Pump Relay" (Connector 1, pin 44). Went out to my truck, and sure enough, there's a pin in the connector at position 44. Looked in the fuse/relay panel, and there's a relay labeled "F/PMP". According to the schematics, C1-44 goes to the underhood fuse block, which it does (Probed C1-44 with a DMM and it comes up to one of the terminals at the "F/PMP" relay). Also according to the schematic, the relay is hooked into the 20A PCM-B fuse, is N/O, and the load side of the relay goes as a grey wire to the fuel pump on the Left side Frame rail, which we all know doesn't actually exist.

So, does it actually do anything or is it just there? If it's just "there", could it be used to control lift pumps instead of "other" 3rd party controllers?

I would like to know this also!

I'm utilizing the Fuel Pump Relay in my 2002. See info below:
http://www.dieselplace.com/forum/showthread.php?t=229228&highlight=fuel+pump+relay

You can do it as modified did it...but IMO at that point why not just have them on a keyed accessory power source? I just have mine wired so when I turn the key on, they turn on. I did put a switch in though, so I can manually turn them off when my fuel tank gets low.

In my installation, I used a +12V when ignition ON source, through an Oil Pressure Switch contact, to energize the Fuel Pump Relay. The fuel pump current load is not on the ignition circuit, but a different fused circuit already intended to run a fuel pump.
Not mentioned, I also wired a toggle switch across the Oil Pressure Switch contact, so if this switch fails, or if I want to run the fuel pump with truck not running, (priming), I can flip the toggle switch.