The engine diagnosis code B1258 shows for error any parts of the car. To identify the problem of the car and to know the meaning of the code, it is essential to know the manufacturer and model of the car. Collect the manual of the car as well for getting solution. However, the code may appear for uncleaned tank. If you do not fresh or clean fuel in the tank. If the tank is empty, you need to clean it and fill with fuel. Dirt is the most common matter of code B1258. If you stock gear with crude gas in the tank, it can be a cause to engine damage.