Here's a strange one. The other day my PM started making this super high pitched dog whistle sound after it starts. You can hear the sound kind of ramp up about 1 second after the motor fires up. It's not super loud but noticeable. My fist thought was either vacuum or electronic. Sounds more electronic to me, kind of like a power supply whistle from a bad cap or something. I can't seem to hear it from outside the van and it doesn't appear to be coming from the dash area. It almost sounds like it's emanating from the cargo area but I haven't been able to pin point the location.