It’s a common scenario for BMW owners: your key fob starts acting up, maybe giving you a low battery warning, or becoming less responsive. The first and easiest fix is usually a battery replacement. Most BMW key fobs use a CR2032 battery, readily available at any drugstore or online. You might think, like many of us, that swapping in a fresh, brand-new battery should solve the problem. But what happens when you diligently replace the battery, only to find your key fob still stubbornly refuses to work? This frustrating experience is exactly what happened to one BMW owner, highlighting a potentially overlooked nuance in BMW key fob battery replacement.
After encountering a key fob error message, this BMW owner proactively decided to replace the battery. Armed with a brand new, unopened Sony CR2032 battery purchased just months prior, and reading a healthy 3.1 volts on a multimeter, they confidently swapped out the old battery. To their surprise, and likely frustration, the key fob remained unresponsive. Thinking it might be a fluke, they tried a second, also unopened, Sony CR2032 battery. Again, the same disappointing result – a key fob that simply wouldn’t communicate with the car.
Seeking professional help, a visit to the BMW dealership in San Francisco unveiled some potentially expensive options. The service advisor presented a tiered approach: first, try a genuine BMW CR2032 battery for $9. If that failed, a $458 diagnostic service to assess the remote. And if the remote itself was deemed faulty, a further $650 for a replacement, on top of the diagnostic fee. Alternatively, they offered a quicker, but still costly, route: try the BMW battery, and if that didn’t work, jump straight to a $650 remote replacement. Faced with a potential bill ranging from $660 to a staggering $1100, the owner understandably started exploring cheaper alternatives, even considering aftermarket options like a Bimmertech key fob at $485.
However, before committing to expensive diagnostics or replacements, the owner decided to take a chance on the seemingly simple first step: the $9 BMW branded battery. Speaking with the parts department, they discovered something quite interesting. The parts specialist mentioned that they frequently encounter customers in the same predicament – replacing the battery with a fresh, aftermarket CR2032, only to have it fail. Intrigued and with nothing much to lose at this point, the owner purchased the BMW battery. And to their relief, it worked! The key fob sprang back to life immediately.
This experience reveals a crucial insight: not all CR2032 batteries are created equal, especially when it comes to powering sensitive BMW key fobs. While the initial Sony batteries tested at acceptable voltages (3.1V and later 3.0V, even dropping to 2.7V after initial testing failure), they simply didn’t function in the BMW key fob. Yet, another Sony battery, tested at 3.0V, did eventually work. This suggests that BMW key fobs might be particularly sensitive to the internal resistance or specific discharge characteristics of different CR2032 batteries, even if they are brand new and reading a sufficient voltage. The success with the BMW-supplied battery, despite the higher cost, points to a level of quality or compatibility that aftermarket batteries might not consistently meet.
The takeaway from this experience is clear and cost-saving: if you’re facing BMW key fob issues after replacing the battery with an aftermarket CR2032, consider trying a genuine BMW battery before resorting to expensive diagnostic services or key fob replacements. It might just be the simple, $9 solution you need to get back on the road without breaking the bank. While the logic behind why some new CR2032 batteries fail while others work remains a bit of a mystery, the practical lesson is invaluable for any BMW owner experiencing key fob troubles.
