Steve, sounds like the remote turn-on lead is very suspect as everyone has suggested here. If I remember correctly, you don't have NAV or DSP, which is exactly like my setup...but I don't recall using that purple/white lead as remote turn-on. I used the solid white lead that is part of the main wire loom that comes from the OEM amp. I know that solid white lead is labeled as ANTENNA in the wiring diagram, but it does get +12V whenever the OEM amp is turned on in all modes (radio/CD/CD Changer/AUX, etc...) and it falls to ground level when the OEM amp is turned off.

It is possible that if you don't ground things correctly, the voltage of the turn-on lead will have no meaning (make sure you ground your voltmeter to the same place that you think your amp is grounded to get proper reading).

Give me a call if you still want to chat about it some more. I got your message, by the way...seems like we've been playing phone tags