On my 07 MDX, which i just purchased two days ago, i linked my iphone just today.
I noticed that everytime i hit the bluetooth call button on the steering wheel, it says its locked. I have to say "0000" to unlock it and then it works fine. It happens all the time i turn on the vehicle.
Its not the same way on my 06 TSX. It will allow you to make a call after you hit the call button directly, no need to enter any code.
Is there a way that I can avoid entering the unlock code everytime

 

Hopefully someone with a 2nd gen MDX can chime in here.

 

By trial and error, found that in that system set up for "Bluetooth", selected the option for No Pin to be used when accessing Handsfree. Its under one of the main menu voice command using the Phone Call button on the steering.

 

You have to turn off the security feature:
1) Press the pick up button and say "System".
2)Press the pick up button and say "Setup"
3)Gothru the menu and when you get to the point where it ask if you want the security feature turned on, press the pick up button ad say "NO".
4)Complete the process and that should take care of it.

"Have fun and enjoy your Acura"