I just bought an '04 A8L. I just noticed that the rear heat can't be controled, and when trying to adjust it from the rear controls the display says "PAS SIV". This displays when pushing any buttons on the rear heat controls. The car did not come with a manual so I'm kind of stumped here. Any ideas?

 

I looked in my Owner's Manual and nothing states "PAS SIV," sorry. You'll have to go to the dealership to find out why. But if I had to guess you need a updated flash for the MMI.

 

A bit late but for future googles you need to turn off the rear window disable feature for the children via the button on the drivers door.