It seems like you can only check 2 of the 3 wires using your test (power and ground). Not sure how you would check the 3rd (signal) wire without some additional info on what that voltage should be.
FWIW, the reason the idle surges is because the IAC is stuck open (or you have a vacuum leak) and ECM cuts off the injectors to limit the idle speed. Have you tired the shade tree fix of tapping on the IAC with a screwdriver or similar tool?
Often the IAC will get dirty and stick, but that usually throws a P505 code not P1519 like you have. I recently had to clean mine after a P505 code.
FWIW, the reason the idle surges is because the IAC is stuck open (or you have a vacuum leak) and ECM cuts off the injectors to limit the idle speed. Have you tired the shade tree fix of tapping on the IAC with a screwdriver or similar tool?
Often the IAC will get dirty and stick, but that usually throws a P505 code not P1519 like you have. I recently had to clean mine after a P505 code.