Well, as a non-electronic old school mechanic I can say the following. My Intercooler pump went at 18,000 miles. It seems the impeller bearing went belly up so there was a distinct "whine" from the pump. The next morning, from cold start through the 15 miles to the dealer where it was replaced ( free ) the whine was constant with no change in pitch to indicate variable speed or voltage just a constant harmonic whine. So my observation would be that the pump must be running when the key is on, unless of course I'm missing something here.