You might find disconnecting all power from the OBC will reset the code, but will loose all the onther setting (date/time/mpg/av.speed/etc...).
I bought a 2nd hand OBC and no code was in it. you set your own by pressing the bott. right CODE button, set a new code using the 1000,100,10,1 keys. You can change this code any or every time that you want to secure the car in this way (the manual explains all)
<span style='color:blue'><span style='font-size:9pt;line-height:100%'><span style='font-family:Arial'>because life's too short not to..........</span></span></span>