Hang in there. We'll get it fixed. I just spoke with the site owner regarding this. He is excellent with GM vehicles. If indicated, it could be the positive battery cable.
Here is what I need you to do. You will need a helper. On the starter motor,
locate the main power supply from the battery to the starter. The main wire is red in color and should have 12v at all times. Confirm that is the case. If it is, have a helper turn the key to the start position while you watch for a voltage drop to the red wire.
I attached the wiring schematic below for your reference.
If there is no change in the voltage to the red wire, have your helper turn the key to the start position again and check to see if there is 12v to the purple wire. This wire should only have power with the key in the start position.
Here is a link you may find helpful:
Let me know what you find.
See pics below. Note: The schematic was only one page. I had to cut it in half to make it readable for you. I overlapped the two pics so you can follow from one to the next.
Images (Click to enlarge)
Tuesday, May 31st, 2022 AT 9:15 PM