andy If the display continually shows four bars " - - - - " then the unit may be codelocked and will need to be left switched on up for up to two hours to reset before another code entry attempt is possible.
Code Entry as Follows:
Switch Radio On - Display Shows " CODE " Then " 0000 " Press preset " 1 " repeatedly for 1st Digit Press preset " 2 " repeatedly for 2nd Digit Press preset " 3 " repeatedly for 3rd Digit Press preset " 4 " repeatedly for 4th Digit If the correct code number is now shown Press Tuning Up Button " ^ " To Enter