If you turn the ignition switch to the OFF position without detaching the front panel, the caution alarm will sound for a few seconds. The alarm will only sound if the built-in amplifier is used. Caution alarm will sound even if beep option is set to OFF under SETUP menu. This is normal operation. Information about Caution alarm and detaching front panel is mentioned on page#7 of the instructions manual:
Yikes! - this is a horrible feature. It is so annoying. Basicly your responce is that you can't turn off the beeping if the face place is attached?! What if you like taking the face plate off when the car is turned off?! I would not have purchased this unit if I had known this was so.
There was no explanations of this feature on the products online description. I will be giving this Sony stereo deck a bad review on the website I purchased it.