New extension harness.  This extends the cam sensor harness from the back of the motor on Gen III LS blocks for use with the cam sensor on the front timing cover from Gen IV LS blocks.  Plug and play. Connects to the extension harness on the timing cover.  If you are using a PCM from a vehicle that originally had a front timing cover mounted cam sensor, you will need to swap pins "A" and "C" on the small extension harness.  If using a 2004 and older PCM, no mods are required