When my 2003 6.0 is off, I have 0.5 amps running thru the GPCM / Alternator cable. With the alternator completely disconnected, there is still a 0.5A draw which points to the GPCM or its harness. Anyone run into this issue or have any ideas?

More pieces to the puzzle. The truck starts and runs fine otherwise. Before I got a DC clamp meter, I hooked up an amp meter after disconnecting both batteries and reconnecting only one, I was seeing around 0.230 A draw but after about 10 minutes, the draw drops to around 0.060 A. I never saw a 0.5A draw. So I'm guessing that if I were to disconnect the batteries again and reconnect them, the 0.5A draw will go away which points to electronics (i.e. GPCM and not the harness).

Thanks