This morning, when i turned the key of my volvo s40, I just hurt a click click click and received a alarm system service required message. What can it be?

 

The 'click, click, click' usually means you need a new battery. See if the car will jump start off another car. If yes then have the battery and charging system tested. Places like Autozone, Advance, etc will test it for free as they want to sell you a new battery.

 

Thanx Hudini, it was indeed the battery.