2001 BMW Key Fob Battery Replacement: A Step-by-Step Guide

Is your 2001 BMW key fob acting up? Do you have to press the buttons multiple times, or get super close to your car for it to work? You might be facing the common issue of a dead key fob battery. While some might believe in urban legends about car batteries recharging key fobs, the reality is simpler: the battery needs replacing. This guide will walk you through replacing the battery in your 2001 BMW key fob, saving you time and money compared to dealership service.

Before we begin, let’s dispel the myth: 2001 BMW key fobs do not recharge from the car. They operate on a small, replaceable battery, just like any other electronic device. When this battery dies, the fob becomes unreliable or stops working altogether. Don’t worry, this is a straightforward DIY task that you can accomplish at home with a few basic tools.

Tools You’ll Need

To successfully replace your 2001 BMW key fob battery, gather these tools:

• Vice-Grips: For securely holding the key.
• Paint Scraper: To start separating the glued fob casing.
• Sharp Knife: For carefully slicing and prying open the fob.
• Small Tipped Soldering Iron: For desoldering and soldering the battery leads.
• Silver Solder: For creating secure solder joints.
• Small Chisel or Pocketknife: To remove old battery leads.
• Wide Jaw Pliers (Channel-Locks): To hold the circuit board (PCB) steady.
• Rubber Band: To apply gentle pressure to the pliers.
• Panasonic VL 2020 Battery (or equivalent): The correct replacement battery.
• Plastic Glue: To re-seal the fob casing.
• Clamps or Rubber Bands: To hold the fob closed while the glue dries.

Step-by-Step Battery Replacement Guide

Let’s get started with the battery replacement process. Follow these steps carefully:

1. Opening the Key Fob

The 2001 BMW key fob is notoriously glued shut. Patience and careful technique are key to opening it without damage.

1. Secure the Key: Hold the metal key part firmly using vice-grips. This provides leverage and stability.
2. Start with the Scraper: Insert the paint scraper into the seam at the ring end of the fob. This will help initiate the separation.
3. Slice and Pry: Carefully use the sharp knife to slice along the seam of the fob casing. Simultaneously, gently pry the case open with the knife or scraper. Work your way around the entire perimeter of the fob, gradually cracking the glued seal.

Image alt text: Close-up showing the process of using a paint scraper and knife to carefully open the glued casing of a 2001 BMW key fob for battery replacement.

2. Identifying the Battery

Once the fob is open, you’ll see the internal components. The battery is located on one side of the PCB.

1. Locate the Battery: Identify the battery well on the key half of the open fob. In the 2001 BMW key fob, the battery is typically a Panasonic VL 2020.
2. Note the Leads: Observe the battery leads. The negative lead is usually positioned at the upper left, and the positive lead comes through at the upper right. Notice that the leads are keyed with different sizes where they connect to the circuit board. This is important for correct orientation during re-soldering.

Image alt text: An internal view of a disassembled 2001 BMW key fob, highlighting the Panasonic VL 2020 battery, circuit board (PCB), and the positive and negative battery lead positions.

3. Removing the Old Battery

Now, we need to remove the old battery. Soldering is required for this step.

1. Secure the PCB: Grip the PCB with the wide jaw pliers (Channel-Locks). Apply a rubber band to the pliers’ handles to maintain gentle pressure. Important: Do not overtighten, as excessive pressure can damage the PCB.
2. Desolder the Leads: Apply the hot soldering iron to the back of each battery lead where it’s soldered to the PCB. Heat the solder until it melts, then gently pull the lead free from the board. Repeat for both leads.
3. Remove Old Leads from Battery: Once the battery and lead combo are free, use a chisel or pocketknife to carefully pry off the custom leads from the old battery. You may need to reuse these leads if your replacement battery doesn’t come with pre-attached leads.

4. Soldering the New Battery

With the old battery removed, it’s time to install the new one.

1. Solder Negative Lead: Solder the negative lead to the bottom (non-writing side) of the new battery. Use a minimal amount of solder to ensure a good fit within the fob casing.
2. Re-solder Negative Lead to PCB: Re-solder the negative lead back to its original position on the PCB. Remember that the negative lead has a smaller through-pin. Double-check the correct orientation before soldering.
3. Solder Positive Lead: Once the negative lead is secured, and the battery is sitting correctly on the white insulating pad on the ‘front’ of the PCB, solder the positive lead. You can start by soldering to either the battery end or the circuit board end.

5. Closing the Key Fob

With the new battery soldered in, it’s time to reassemble the key fob.

1. Clean Up Fob Edges: Remove any frayed edges or excess glue from the fob casing halves to ensure a clean closure.
2. Test Fit: Before applying glue, test fit the fob halves together without the PCB inside. Ensure they mate correctly.
3. Apply Glue: Apply a thin, even bead of high-quality plastic glue to the perimeter of one fob half.
4. Reassemble and Clamp: Carefully place the PCB back into the fob half and mate the two halves together. Use clamps or rubber bands to hold the fob firmly closed while the glue dries completely, according to the glue manufacturer’s instructions.

6. Re-sequencing the Key Fob

After replacing the battery, you’ll need to re-sequence your key fobs to your BMW.

1. Prepare Keys: Gather all your BMW key fobs. Choose one key to designate as the ‘initial’ key (e.g., a key that is usually kept at home).
2. Enter Car: Get inside your BMW with all doors closed and unlocked.
3. Initial Key Sequencing: Insert the ‘initial’ key into the ignition and turn it to position 2 (dash lights on, but engine not started). Remove the key.
4. Button Press Sequence: Immediately hold down the unlock button on the key fob. While holding unlock, press the lock button three times in quick succession. Release all buttons. The car’s Central Locking System (CLS) should respond by locking the doors and then unlocking the driver’s door.
5. Repeat for Other Keys: For each remaining key fob, repeat the button press sequence (step 4) after the initial key sequencing.

Important Note: Any key fob you own that is not re-sequenced during this process will not function correctly. You will need to repeat the entire re-sequencing procedure to include any missed keys.

Conclusion

Replacing the battery in your 2001 BMW key fob is a manageable DIY task. By following these steps and using the right tools, you can restore your key fob’s functionality and avoid costly dealership fees. Remember to take your time, be careful with the delicate components, and enjoy the satisfaction of fixing it yourself! Now you can drive off, confident that your key fob is working perfectly.