Unless that is, the display still shows "Radio locked" as soon as you turn the key. That means you've entered the wrong code too many times. The solution is to use the spare key to turn the ignition to A (one click) and leave it in this state for a whole hour. Since you still have the main key handy, lock the car up and go and have a cup of tea. If you only have one key, sit in the car and read a book for an hour.
At the end of this period the central display should be asking you for the code. Enter the right code and all will be well. Then write the code down somewhere you'll remember it if required again.
A.R.S., November 2012
