I believe it has a silver/gray cover on it, and it is the sensor with three wires going to it, not two. The two wire plug is the IPR.
And since you asked what ICP is and what it does, and since I really had no clue, I took this from a tech from another forum:
ICP stands for Injection Control Pressure. You first need to understand that the injectors in the 6.0L use high pressure oil to operate. The amount of fuel delivered to the cylinders is directly proportionate to the pressure in the high pressure oil system. The higher the oil pressure is, the more fuel that is injected into the engine. The PCM controls this pressure by controlling a regulator (IPR) and uses the ICP sensor to provide a feedback signal to the PCM indicating the injection pressure.
The injection process is actually is a little more complex then that but I wanted to keep my reply related to ICP. The ICP sensor also provides information to the Fuel Injection Control Module to calculate injection timing and it also allows the PCM to monitor the condition of the high pressure oil system.
This will probably help you out a lot too... 03/ Early 04 ICP Swap - Ford Truck Enthusiasts Forums