D1 or two ? On D1 its the same one in many rovers so any handbook will give you the routine . Like the guys say , there is a time period that doubles each time a wrong code is entered , the book says do NOT turn off between trys , their emphasis .
from handbook , with some clarification by me (thats a laugh) , entering security code ...
switch on radio , "code" appears in display , press preset button 1
press one of the two tuning buttons (arrows , numbers up and down) to select first number . Press preset button 1 to store first digit . Next space starts flashing .
use either tuning button (arrows) to select second digit of code . Press preset 1 to store . Next space starts flashing .
select third digit using tuning arrows . Press preset 1 to store . Next space starts flashing .
select final digit using tuning arrows . Display now shows full 4 digit code . Press prest button 1 to store .
If correct code is entered radio sounds 2 tone bleep (sadly , not The Specials) and radio will operate .
If wrong code is entered "err" shows in display , do not turn off , wait until "code" shows , then start process again .
If you have CD changer under drivers seat ( I once drove for 2 months before I realised there was one there) then this will come on with the radio .
Hope this helps .