A car radio code is a short series of numbers that is associated with a security feature found in some head units. Its purpose is to prevent theft by rendering a stolen head unit inoperable when it is disconnected from the battery. However, this feature will also work if your battery is dead. In either case, you will need to enter the code to get the head unit working again. Your typical radio will flash "CODE" to indicate this.

There are several ways to find the code for a car radio, but these are the main ones, in descending order of complexity and cost.

In some cases, you can find the radio code in the owner’s manual. This isn’t a particularly secure place, as most people keep their manuals in their vehicles, but some manuals have a place for it. If you bought your car used, the previous owner may have entered it there.

Check the websites of your car manufacturer and the stereo manufacturer. Companies sometimes maintain online databases of car stereo codes. Entering information such as your vehicle identification number (VIN) or the radio's serial number may yield the code you're looking for.