Is your 2002 BMW key fob becoming less responsive? Do you have to press the buttons multiple times or stand right next to your car for it to work? It might be time for a battery replacement. Many BMW owners experience this issue, especially with older models like the 2002 series. The urban legend that these key fobs recharge from the car’s operation is unfortunately false. There’s no inductive charging or direct electrical connection for recharging the key fob battery while driving. The culprit is simply a depleted battery. This guide will walk you through replacing the battery in your 2002 BMW key fob yourself, saving you time and money compared to dealership service.
The key fob for your 2002 BMW is designed to be sealed, but with a few common tools and a little patience, you can access and replace the battery. This DIY repair is straightforward and can restore your key fob’s functionality quickly.
Here’s what you’ll need to replace the battery in your 2002 BMW key fob:
- Vice-grip
- Paint scraper
- Sharp knife
- Small tipped soldering iron
- Silver solder
- Small chisel or pocketknife
- Wide jaw pliers (Channel-Locks)
- Rubber band
- Replacement battery: Panasonic VL2020 with tabs (or a plain VL2020 battery)
- Plastic glue
Step-by-Step Battery Replacement Process:
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Opening the Key Fob: The first challenge is to open the glued-shut key fob. Start by using the paint scraper at the key ring end of the fob. Securely hold the metal key part with the vice-grip. Carefully use the sharp knife to slice along the seam of the fob, gently prying it open as you go. Work your way around the perimeter until you can crack the case open. Be patient and avoid damaging the internal components.
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Identifying the Battery: Once open, you’ll see the internal components. The battery is located on one side of the PCB (Printed Circuit Board). In the 2002 BMW key fob, the original battery is often a Panasonic VL 2020 with custom leads spot-welded to it. You can purchase a replacement VL2020 battery online. While replacements with pre-attached leads are available, using a plain battery and soldering the original leads back on can sometimes be easier for a tighter fit.
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Removing the Old Battery: To remove the old battery, you’ll need your soldering iron. Secure the PCB using the wide jaw pliers and apply a rubber band to the handles to maintain gentle pressure – be careful not to clamp too tightly and damage the board. Apply heat from the soldering iron to the back of each battery lead where it’s soldered to the PCB. Once the solder melts, gently pull the battery lead free. After both leads are detached, use the chisel or knife to carefully pry the custom leads off the old battery.
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Soldering the New Battery: Solder the negative lead (the one with the smaller through-pin) to the bottom (non-writing side) of the new VL2020 battery. Use a minimal amount of solder to ensure a good fit within the fob. Then, resolder the negative lead back onto the PCB, ensuring it sits correctly on the white insulating pad. Next, solder the positive lead to the top of the new battery and back to its corresponding point on the PCB. Double-check the polarity and lead orientation before finalizing the solder joints.
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Reassembling the Key Fob: Before gluing the fob back together, clean any rough edges on the plastic case for a better seal. Test fit the two halves of the fob without the PCB to ensure they align properly. Apply a thin bead of plastic glue to the perimeter of the fob case. Carefully place the PCB back inside, align the two halves, and clamp them together using clamps or rubber bands. Allow the glue to dry completely according to the manufacturer’s instructions.
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Key Re-sequencing: After replacing the battery, you’ll need to re-sequence your BMW keys to your car. Here’s how:
- Get all your BMW key fobs.
- Inside your car, close and unlock all doors.
- Insert the first key into the ignition and turn it to position 2 (dash lights on, engine off).
- Remove the key.
- Immediately hold down the unlock button and press the lock button three times in quick succession.
- Release all buttons. The car’s central locking system should respond by locking and then unlocking the driver’s door.
- Repeat the button pressing sequence for each additional key fob you have.
Any key not re-sequenced during this process will not function correctly and will require you to repeat the entire re-sequencing procedure for all keys again.
With the battery replaced and your keys re-sequenced, your 2002 BMW key fob should be working like new again. Enjoy the convenience of a responsive key fob and the satisfaction of a successful DIY repair!
