What Is That Noise?
 

OK, if I put the key in the ignition, and turn it, to say, check the oil level, and not actually start the engine, I can hear very subtle sounds in the dash. Almost sounds like a computer booting-up. I don't have PCM. What are these sounds?

It's the sound of the CD in the player 'engaging'.

SD987, there is not a CD in the drive.

I am going to guess that the noise is the Bose amps turning on or the PSM turning on.