You are able to program a 2005 Mercury Grand Marquis Key by yourself if you have two original working keys that start your vehicle. The new key will first need to be cut to match your original at a local automotive locksmith or dealership. Once the chip key is cut, you can use the printed programming instructions that we send to make the key work for your vehicle. The instructions are very easy to understand and can be performed in less than a minute. If you only have one or you lost all working key for a 2005 Mercury Grand Marquis , the programming can only be done at the locksmith or dealership that cuts the key for you.