My car has the dealer option Sirrus radio tuner. How do I select this input? The owners manual does not mention it.

 

It's tuned to a certain FM frequency as there's a FM Modulator built-in to the Sirius unit. In the Sirius display, you should be able to scroll through it's menu and find something that says "Frequency" or something like that. In there, you can turn the Modulator on or off, and you can set the frequency to your liking. Then tune your FM radio to that frequency and you should be good.

 

Btw, I found out that the "Lifetime" Sirius subscription only applies to the original owner. The dealer can get you on a 3 month trial, and then it goes away, forcing you to pay Sirius to keep the subscription. I didn't bother subscribing after the trial ran out.

 

How do they know? The one in my A8 has worked for 18 months.
BTW, thanks for the help with using. I kept looking for a button to select AUX input. Forgot about the FM modulators. Never would have figured it out.