Okay, this is urgent for me. I've got the same issue and I can't seem to find the solution. I took my engine apart to do a cooling system overhaul.
I'm stealing cooljess' picture for this. I have my two red cables connected to the post #1. I never touched post #3. The thinner black wire is connected to post #2. The thicker black wire is connected to post #4.
I get 12V between post #1 & #2.
I get 12v between post #1 & #3.
I never get any voltage between #1 & #4. I can leave the key off or on, nothing happens.
I tested all the fuses and they are all continuous, not blown.
Why am I not getting any power between posts #1 & #4?
Can INPA or DIS/GT1 read what is going on?