Safe mode?

Hi can any one please help me,i removed my radio 2 years ago but my cd player recently stop working so i replaced it putting my original phillips car 400 back in, It came on SAFE as expected,but it will not allow me to enter the code, i have followed the book guide holding AS then power on but theres no beep and no cange in the display eg safe 3.This is unique as i have had no atemps to enter thecode either before or now, i have tried just leaving it on safe for a while but still no change.Any help would be greatfully apreciated thanks.