If the head unit doesn’t work and the display reads SAFE or CODE, then the memory has been lost (usually after a battery disconnect) and the anti-theft protection is activated. The display should show "SAFE" or "CODE" then revert to four dashes after 3 or 4 seconds at power on (if you haven't put a code in recently). Enter your code at this point (when the 4 dashes are shown), then press the smart symbol button to confirm the code. The radio should be activated. Example - if your code is 4321 you would get the 4 dashes to show and then press the "1" button x4 four times, the "2" button x3 three times, the "3" button x2 twice times and the "4" button x1 one time. It’s a bit like text messaging using 1 button for multiple options. Then press the Smart symbol button once after all digits are correct. If you get it wrong, the unit will go into a wait state showing SAFE again (not allowing any more input) for an increasing time (starts at 20 seconds or so ) , you can do this up to 7 times by which time the wait period before it lets you re enter a code is 24 hours before you can put another sequence in - using the 4 station pre-sets. If you don’t have a code or it's not correct then you need to apply to a main dealer for a radio code, V5 registration docs and ID will be required usually and a fee usually about £30 depending on each dealer.