Is your BMW E46 key fob becoming less responsive? Do you find yourself pressing the buttons multiple times or needing to be right next to your car for it to work? It might be time for an E46 Key Fob Battery Change. Many E46 owners experience this issue, and thankfully, it’s a straightforward process you can tackle yourself. This guide will walk you through replacing your BMW E46 key fob battery, saving you time and money compared to dealership service.
Recognizing the Symptoms of a Dying E46 Key Fob Battery
Before you dive into the battery replacement, it’s helpful to confirm that a weak battery is indeed the culprit. Here are common signs that your e46 key fob battery needs changing:
- Reduced Operating Range: You need to be closer and closer to your BMW for the key fob to lock or unlock the doors.
- Intermittent Functionality: Buttons require multiple presses to activate the desired function (locking, unlocking, trunk release).
- Complete Failure: The key fob stops working altogether, even when standing right next to the vehicle.
If you’re experiencing these issues, a battery change is likely the solution. Let’s get started with the tools you’ll need.
Tools Required for Your E46 Key Fob Battery Replacement
To successfully perform your e46 key fob battery change, gather these tools before you begin:
- Vice-Grips: To securely hold the key during opening.
- Paint Scraper: For initial prying of the glued fob casing.
- Sharp Knife: A utility knife or similar for carefully slicing along the fob seam.
- Small Tipped Soldering Iron: For precise soldering of the battery leads.
- Silver Solder: For creating secure electrical connections.
- Small Chisel or Pocketknife: To remove old battery leads.
- Wide Jaw Pliers (Channel-Locks): To hold the PCB steady during soldering.
- Rubber Band: To apply gentle pressure to the pliers.
- Plastic Glue: To reseal the key fob casing.
- Replacement Battery: Panasonic VL 2020 with or without leads (more on this later).
With your tools assembled, let’s move on to the step-by-step process of replacing your e46 key fob battery.
Step-by-Step Guide to E46 Key Fob Battery Replacement
Follow these steps carefully to change the battery in your e46 key fob:
Opening the Key Fob
The E46 key fob is notoriously glued shut, so opening it requires patience and care.
- Secure the Key: Grip the metal key part of the fob firmly with your vice-grips. This provides a stable base to work with.
- Initial Separation: Start at the ring end of the fob. Use the paint scraper to wedge into the seam and gently begin to separate the two halves.
- Slice and Pry: Carefully use your sharp knife to slice along the seam of the fob casing. Alternate between slicing and gently prying with the knife or scraper to gradually crack the case open. Be patient and avoid applying excessive force to prevent damage.
Battery Identification and Removal
Once the fob is open, you’ll see the internal components.
- Locate the Battery: The battery is a Panasonic VL 2020, typically with custom leads welded to it. Note its orientation and position within the fob.
- Prepare for Soldering: Use your wide jaw pliers to grip the Printed Circuit Board (PCB). Apply a rubber band to the pliers handles to maintain gentle pressure, securing the PCB without over-tightening.
- Desolder Old Battery: Apply your hot soldering iron to the back of each battery lead where it connects to the PCB. Wait for the solder to melt, and then gently pull the lead free from the board. Repeat for both leads to remove the old battery and lead assembly.
- Remove Custom Leads (If Necessary): If your replacement battery doesn’t have pre-attached leads, use your chisel or knife to carefully pry the custom leads off the old VL 2020 battery. You will reuse these leads.
Installing the New Battery
Now, it’s time to install your new e46 key fob battery.
- Solder Negative Lead: Solder the negative lead (the one with the smaller pin) to the bottom (non-writing side) of your new VL 2020 battery. Use a minimal amount of solder for a clean connection and to maintain a tight fit within the fob.
- Resolder Negative Lead to PCB: Carefully re-insert and solder the negative lead back into its original position on the PCB. Ensure correct orientation by checking the pin sizes and markings on the board. The battery should now sit centered on the white insulating pad on the PCB’s front side.
- Solder Positive Lead: Solder the positive lead to the top of the new battery and then back to its corresponding point on the PCB. The order doesn’t matter if the negative side is correctly connected.
Closing the Key Fob
With the new battery installed, it’s time to reassemble and seal the key fob.
- Prepare the Casing: Clean any frayed edges or excess glue from the fob casing halves to ensure a clean closure. Test fit the halves without the PCB to confirm they mate properly.
- Apply Glue: Use a brand-new, high-quality plastic glue. Apply a thin, even bead of glue along the perimeter of one half of the fob casing.
- Reassemble and Clamp: Carefully place the PCB back into the fob half and align the two halves of the casing. Press them firmly together and use clamps or rubber bands to hold them securely while the glue dries according to the manufacturer’s instructions.
Re-sequencing Your E46 Key Fob
After the e46 key fob battery change, you may need to re-sequence your key fobs to ensure they communicate correctly with your BMW.
- Prepare Your Keys: Gather all your E46 key fobs. Designate one key as the “initial” key for clarity during the process.
- Enter Car and Close Doors: Get inside your BMW, close all doors, and ensure the doors are unlocked.
- Ignition Position 2: Insert the initial key into the ignition and turn it to position 2 (dash lights on, but engine not started).
- Remove Key and Button Press: Remove the key from the ignition. Immediately press and hold the unlock button on the key fob. While holding unlock, press the lock button three times in quick succession. Release all buttons.
- Confirmation: The car’s Central Locking System (CLS) should respond by locking the doors and then unlocking the driver’s door, confirming successful sequencing.
- Repeat for Other Keys: For each additional key fob, repeat step 4 (button press sequence) within 30 seconds of the previous key.
Any keys not re-sequenced during this process will not function correctly and will require repeating the entire re-sequencing procedure for all keys.
Conclusion
Congratulations! You’ve successfully completed an e46 key fob battery change. By following these steps, you’ve restored the functionality of your BMW key fob and saved yourself the expense of dealership service. Enjoy the convenience of a responsive key fob once again.
