How do I know if ANC is working or not?
I know it is working by default, I tried turning it off and on,block the two front mic, do not hear any difference.

I had a 2009TL as a loaner, same thing, using the diag mode I changed between ANC off and on, do not hear any difference.

 

ANC is always on. If the car is running, and you put your finger or thumb tightly over the front mike, you will hear the ANC working out of phase; a bunch of subwoofer pulses that will disappear immediately after you remove your thumb from the mike.

And as Tampa noted in previous thread, don't be surprised if this is moved to the Audio Navigation Electronics section

 

there are two mics at the top, tried to block both, no difference, didn't hear anything.

 

Dealer time, unless you put your thumb over the wrong mic, not the HFL mic. The ANC mic is a small plastic square in the headliner with hole in it. There is a similar one in the rear near the reading light

 

OK, found it.
Now When I put my ignition in Accessories mode, turn the diag on using the radio 1 - 6 buttons, choose ANC off I hear a continues ham from the speakers.

 

I can only really tell the difference at hwy speeds. With radio turned up to about 15, put your finger over the square on the headliner, just in front of the controls where the garage openers are. I can hear a distinct rumble when I do this, almost as if there is more hwy noise. When I take my finger off of it, it gets quiet.

 

I did some tests today, blocked the hole and payed more attention to the noise.
When plugging the hole you can hear the exhaust and engine noise that the ANC masks.
Even closing the ANC during drive using the radio diagnostics brings up the low level noise.

 

funny - I notice the difference the most when stopped at idle and then acceleratung. Hardly notice at all at highway speed, but mine is 05 and I think they improved ANC in newer models