A:Answer I do not know. I know that on my Kenwood BT 772HD, shutting off the ignition and withdrawing the key has no effect on the various radio unit presets.
I also had the unit back to Best Buy for servicing a week and a half after it was installed. Tech did the safe and smart thing and oulled the negative battery cable.
All presets and programming, stuff from clock / calendar, to every bit of programmed features preferences all disappeared.
Also killed the Sirius.
Very frustrating.
I've never just disconnected a ' 'yellow wire" so I don't know the specific answer to your question. However from the unit behaviour I saw with the disconnection of the negative battery terminal I have to assume that the unit is a "vampire unit"; that neither shutting down the engine and removing the ignition key or using the unit's shut off button interfere with presets and programming so the unit somehow keeps power. It may be the "yellow wire" of which you asked, but I have not observed that directly. Certainly killing all electric power by removing a cable from the battery does mess up the unit's presets.
Note you dod not spwcify a manufacturer or model number in your question,: my answer directly applies only to the Kenwood BT772HD. I suspect the same results would happen with other models / manufacturers.
