Many car manufacturers install radios in vehicles that have a theft-deterrent feature that deactivates the radio when the radio loses its power source. This can happen when the radio is stolen, or the battery dies or is disconnected. The radio stays inactive until you enter the proper reset code. The reset code is provided to the buyer when the vehicle is first sold. If you do not have the card or code, you can retrieve the code from a dealership.
Get the vehicle identification number (VIN). This is available from the title, registration or a VIN plate on the dash next to the bottom corner of the driver side of the windshield.
Contact the parts and service department of a dealer of the car's manufacturer. If the manufacturer has more than one vehicle line, like General Motors, you can contact any dealership for the manufacturer.
Provide the vehicle VIN and proof of ownership, if required. Visiting the dealership in person with registration or proof of ownership may be required.
Request the vehicle's radio code and record it for future use.
Some companies, like Honda/Acura, provide radio codes online if you are the owner of the vehicle listed in the company's database.