A flat battery in your BMW key fob could make it difficult or even impossible to access your vehicle. If this happens to you, replacing the battery is a quic Now that you understand the reasons for changing the battery in your BMW X5 key fob, let’s go over the steps to replace it. Step 1: Remove the key from the fob. There’s a small metal button located above the key part of your key fob. Press the button and pull out the key. Step 2: Open the fob. A: In short, to replace a BMW X5 key usually cost between $350-$1000. It depends on a few factors: Type of key. The year manufactured. Time of day & your location. Where you get a key replacement (dealer, automotive locksmith, online, etc.) Availability of code to cut a new key. Original ignition or not. 2. Insert the key blade or a flat blade screwdriver into that small hole from the right side to remove the cap. 3. Remove the old battery using a flat blade screwdriver. 4. Install the new battery back in the place. 5. Put the cover back on the key fob. If you have any suggestions about new tutorials, let us know in the comments section! The remote entry uses a battery that is charged during driving. If the 'spare' key is seldom used it may have lost sync with the rolling codes. To re-sync there is a process that involves turning the ignition on then off, removing the key, holding unlock and tapping three times on the BMW logo. The doors lock and unlock to indicate success. IQQM0u.