when the battery is disconnected, your Renault radio is locked by a four digit code.
You'll need to re-enter the radio security code.
If you've lost Renault radio code, you can recover it with this app.

Guide:
* Remove the stereo from the dashboard.
* Search the unit serial number (1 letter and 3 digit) EX:V438
* Input serial number in the application
* Click the Generate Code Button
* Enter the generated code in your radio.