It does need a code unfortunately, first off, go back to the person you bought it from and see if they have the code, if that fails ask for your money back. It also depends what vehicle it came out of and how old it is, some newer manufacturers head units are "paired" to the vehicle and the only way to un-pair them is to take it in to the stealership, on the other hand it maybe worth looking on line to see if you can find a decoding specialist for the unit you have.