How to Replace the Battery in a Mercedes-Benz E240 4MATIC Key?
2 Answers
To replace the battery in a Mercedes-Benz E240 4MATIC key, follow these steps: 1. Insert a flat-blade screwdriver into the contact slot on the back cover and pry it open to separate it from the wireless remote. 2. Insert the screwdriver into the middle of the contact slot, turn it a quarter turn, and pry open the back cover of the electronic key. 3. Install the battery with the positive terminal facing upwards into the back cover of the wireless remote, then press the cover plate to secure it in place. Below are some precautions for replacing the smart key in a Mercedes-Benz E280 diesel version: 1. Do not touch the circuit board or battery terminals. 2. Although the remote is waterproof, if it gets wet, it should be dried immediately. 3. When replacing the battery, ensure that the electrode contact points are free from dirt, grease, and other foreign objects.
I recently replaced the battery for my Mercedes-Benz E240 4MATIC key, and it was actually quite simple and not troublesome at all. There's a small gap on the back of the key—usually, you can gently pry it open with a flat, hard card like an old bank card or a small screwdriver. Just be careful not to use too much force, or the casing might crack. Inside, it uses a CR2025 battery, which you can easily buy at a supermarket or online for just a few bucks. Remove the old battery, align the new one correctly with the positive and negative markings, press it in firmly to ensure good contact, and then snap the cover back on, pressing it securely with your fingers. Finally, test the lock and unlock functions by pressing the buttons to make sure everything works. The whole process takes about five minutes. I was worried about breaking it the first time, but it turned out to be super easy. I recommend proactively replacing the battery every two years or so to prevent sudden failures, like getting stuck in the rain at night. It saves both money and time—way better than rushing to the dealership.
