I have a 2002 TL Type S. I lost power to my battery so my radio was reset and I needed the code. I went to the dealer and they retrieved my Radio serial number by pressing 1 and 6 on the radio simultaneously and then while holding 1 and 6, pressed the radio power button. A 4 digit code appeared and then another 4 digit code appeared on the radio display. Together, this is the 8 digit serial number that the dealer needed to retrieve my radio code from their database.

Before you can try this trick, make sure that the radio display reads "err1".

 

every year and model is different- that trick does work on a few years
Write the codes down - you can store them secure for free on your acura.com account
Everyone should be registered there anyway
https://www.ahm-ownerlink.com/login.asp?brand=acura