Man you can have it all! I'm itching to get some work done.
Are you ready to have some fun?
Recording the battery voltage before starting any tests is a good habit to get into.
Test 1 - Key ON Engine OFF - Touch both sides of the TAC fuse. If voltage is above 12v, move on to test 2.
Test 2 - Key ON Engine OFF - Black lead of meter to battery negative, red lead of meter to yellow wire at throttle body connector. I'm using a t-pin. You can unplug the throttle body connector to test, but do
not force the probe into the connector pin.
Do the same thing for the brown wire in the throttle body connector.
So, in my 03, I've verified voltage through the TAC fuse, and since I have voltage at both TAC wires at the throttle body, I know the pcm input/outputs are ok. If you don't have voltage in either (or both) of the TAC wires at the throttle body, I'll unplug my pcm and show those. I try not to unplug things unless it's necessary.
This is my version of the DIY starting point for p1512. The test numbers are from the OEM service info, the numbers in parentheses are my order. So (1) Check the TAC fuse (2) check the TAC circuits at the throttle body. If voltage is present at the TAC wires in test 2, I skip (3) and go to (4) check for a sticky/stuck/broke tbody. We could go further by using a super test light to load down the TAC throttle body wires, but usually TAC issues are from broken wire(s) in the wiring harness.
Your mission, if you choose to accept it, is to test and record your voltage at the TAC fuse, and TAC wires at the throttle body. Those results will tell us where to go next.