Did this issue happen after a or a dead battery ?
If you cannot access the menu because the screen is totally frozen or asking for a code you do not know, you can perform a physical reset.
Check your original Grundig user manual box for a printed security card.
: Release the button and wait for the unit to restart. You should see the Grundig logo appear. Grundig GX3800 Factory Reset Codes
(Commonly used for "Factory Settings" menus on similar head units). 123456 (A common 6-digit variant).
To factory reset your car stereo, you can typically use the software reset option within the settings menu. If the system requires a security code or PIN for specific operations like Bluetooth pairing or accessing deeper settings, the default codes are often 0000 or 1234 . Factory Reset Steps
Once you have the serial number, you can use one of the many online Grundig radio code calculators to generate the correct code. These are widely available by searching for "Grundig radio code calculator" or "Grundig code generator". Websites like radiocodescalculator.com offer such tools.