The ignition of your Mercedes E320 contains a specific code that is used when programming your keys to ensure that your keys open and start only your E320. When you purchase a new or additional Mercedes key for your E320, it must be programmed with your vehicle before it will work. The programming process is easy, and you can do it yourself in just a few minutes.
Place your new key into the ignition of your Mercedes E320.
Hold down the "Lock" button on the key fob.
Remove the key from the ignition while maintaining your hold on the "Lock" button.
Push the "Unlock" button on the key fob five times, consecutively. Do not release your hold on the "Lock" button while pushing the "Unlock" button.
Release your hold on the "Lock" button to complete the programming process.
Call Mercedes if you have trouble programming your keys.