Key Fob Battery Low Warning - please help

[Polly Wog]

I’ve been a Model S owner for nearly 7 years, and I’m stumped on the problem I’m having now. In my 2019 Model S, both key fobs started generating the “key fob low battery” warning on the same day. I did a MCU reboot with no change. I then replaced the battery in one fob, with no effect - the warning remains. Fast forward 2 months. 3 days ago, while driving my original 2014 Model S that we keep on the mainland, the “key fob low battery” warning appeared. Because I figured it had been a year since it had been replaced, I put a brand new battery in the key fob. No luck, the warning remains. My wife then told me that she started getting the same warning with her key fob on the same day! Once again, I did a MCU reboot with no change. I also did an IC reset, with no change.

Does anybody here in Tesla land know what to do about this? A service appointment seems ridiculous, but I don’t know what to do. It is super annoying! Thanks!

 

[Akikiki]

@Polly Wog, The fobs don't behave these last few years as they did in the early years. What does that mean ??
Its customary these days that after you replace the battery in one, you need to take both fobs (even the one that you did not change) to the car. Sit in the car with both and reboot the center console. Usually, (not always), but usually this has cleared the message. If it does not give it a little time, like roll down a window, and leave both in the car for a short time and come back and try again.

Why this is happening only Tesla knows. When exactly did this start? Not sure, but its been going on a while. I think you might ask then, why doesn't it need both when the SC replaces just one battery because they have only the one fob. I don't know their secret. I asked once, and never got an answer between asking the SA and getting the tech to answer.

However give the two present fobs in the car trick a try.

 

[Polly Wog]

@Akikiki, Although it took the entire day, and getting in and out of the car many times, it seems that your suggestion worked! Thanks!

 

[Akikiki]

Welcome. Glad to be of a little help.

 

[doghousePVD]

There are a lot of fake (counterfeit) batteries coming from China. I’ve ended up with some from Amazon, branded Samsung. They work for a short time then have low voltage. Very frustrating.

Try using other batteries from another source.

 

[Bruinfan]

have been having the same message for 2 months now. 2016 Model S. Replaced battery with regular energizers from the supermarket... will try the above method.

 

[Replayray]

2017 MS 100D. I had the same issue. New batteries in both key fobs, soft and hard reset, same "Low key fob battery".
I took both key fobs and placed them in the center console. After about 10 seconds, the "
Low key fob battery" message went away. Yay!!!

 

[Justmurr]

I just love having this forum to come help give solutions for these little things that happen.

The key fob battery low alert was driving me irrationally crazy…it really should be the type of alert that I could acknowledge to hide it for each drive until I fixed it but nooooo..this alert took some work to go away….first I tried switching to my 2nd, basically unused fob…nope…still there…so I went out and got 2 fresh batteries (the user manual does say you should replace both or all fobs at the same time)…replaced both fobs (in the house)…took 1 out for a test…nope…annoying alert still there…ok, so let me try the other fob, maybe I got a bad energizer?…..nope….still have to look at this annoying alert…which is extra annoying if you have FSD btw…so then I come here to the forum for some research….and WAH-LAH!
Taking BOTH fobs into the car at the same time and placing them in the console area together did the trick!
Thank you Tesla forum! Time to go for a nice FSD beta drive

 

[hybridbear]

We have had a persistent low key fob battery message start now on our 2016 S90D on FSD Beta 11.4.7 (2023.7.30). It only happens with key fob 1. It just started with installing the aforementioned software version. Replacing the battery did not clear the message. The message had come & gone on its own the first few days but now it’s persistent anytime key fob 1 is in the vehicle. Any ideas? Does the center console trick mentioned above involve updating key fob firmware? I believe there's a step in the menu to do that.

 

[Akikiki]

We have had a persistent low key fob battery message start now on our 2016 S90D on FSD Beta 11.4.7 (2023.7.30). It only happens with key fob 1. It just started with installing the aforementioned software version. Replacing the battery did not clear the message. The message had come & gone on its own the first few days but now it’s persistent anytime key fob 1 is in the vehicle. Any ideas? Does the center console trick mentioned above involve updating key fob firmware? I believe there's a step in the menu to do that.

Yeah. In case this has not been covered recently, last time we went through this, the trick is - both fobs. Move both fobs into the car at the same time. (Useful to change both batteries at the same time, but not required.) With both fobs in the car at the same time, within a minute or so, the car will clear the message. If it does not withing a couple of minutes, reboot the car.

 

[hybridbear]

Yeah. In case this has not been covered recently, last time we went through this, the trick is - both fobs. Move both fobs into the car at the same time. (Useful to change both batteries at the same time, but not required.) With both fobs in the car at the same time, within a minute or so, the car will clear the message. If it does not withing a couple of minutes, reboot the car.

What we've noticed so far is that with both fobs in the car the message goes away after a few drive cycles. Same is true with only fob 2 in the car. But with only fob 1 present the message appears again. And replacing the battery in fob 1 didn't make a difference.

 

[doghousePVD]

Complicating matters is many batteries sold on Amazon are knockoffs or partially discharged. I had two shipments of the Tesla batteries fail intermittently. Got some from a Batteries Plus store, worked like charm.

I’m not affiliated in any way with that store. You can Google search for battery scans on Amazon.

 

[Akikiki]

What we've noticed so far is that with both fobs in the car the message goes away after a few drive cycles. Same is true with only fob 2 in the car. But with only fob 1 present the message appears again. And replacing the battery in fob 1 didn't make a difference.

If I were in your shoes, since this is odd behavior, I would sit in my car with both fobs and swap the batteries between both fobs. To me that's a simple test of the fob (which likely has no problem) and test that new battery. I like and agree with what @doghousePVD , regarding knockoffs. I keep learning to not buy a large card of 2032's and expecting the last few to still be good after I have let them sit in a drawer for too long.

 

[hybridbear]

If I were in your shoes, since this is odd behavior, I would sit in my car with both fobs and swap the batteries between both fobs. To me that's a simple test of the fob (which likely has no problem) and test that new battery. I like and agree with what @doghousePVD , regarding knockoffs. I keep learning to not buy a large card of 2032's and expecting the last few to still be good after I have let them sit in a drawer for too long.

Thanks for that idea. I have replaced the battery twice in fob 1. First with an Energizer brand 2032 that was the last of its pack, and then with a Duracell 2032 which is from a new pack. The message still always appears with fob 1. I have not yet replaced the battery in fob 2. Previously the message would disappear when driving with only fob 2 present, but as of yesterday it is not disappearing. I have more Duracell 2032s which are from a new pack which I could try. The only time the message has gone away with fob 1 present was when I tried doing the "fob update" under the Service menu & then we started the car with both fobs together in the center console.

 

[Phil Stasik]

It’s interesting that so many of us have this same issue, and there seem to be several solutions. Our 2020 MY has only one fob, and it’s been 3 years, 3 months since new. We only used the fob once, when new to confirm that it works. We only use our phones as keys. Today, we got the “Key Fob Battery Low” warning, which prevented us from using Summon to park our car in the garage. Again, we always use our phones to control Summon for parking.

The fob works normally, but I’ll play the game.

After reading numerous excellent reports here, I:
1) Removed the original Panasonic 2023 (3.02 Volts), and replaced it with an Energizer 2023 (3.15 Volts). The fob continues to work well, but the warning message persisted.

2) Brought the fob, both phones, and our keycards, as well as our key card ring out to sit on the console. The warning persisted.

3) Looked through the Locks>Keys page on the User Interface, and un-installed the fob. The warning persisted. This also gave me a chance to clean-up some duplicate entries, and provide better names for each key.

4) Re-installed the fob. The warning persisted.

5) Did a two-button reboot. The warning persisted.

6) Manually parked the car (risky in tight garage), and plugged in to our Level 2 EVSE.

Finally, the warning went away!

The fact that the software tastes “low voltage” (3.02V) on an unused, but in-range fob, then locks an un-clearable warning message on the vehicle is a bug. This message should not persist with the fob out of range, nor should it persist after a nominal voltage battery is installed. The message should not lock out the Summon function, when a phone is controlling the Summon.

I put my fob into a Farady bag to prevent recurrence, but the signal was strong enough to penetrate the bag, so I wrapped the damned thing in aluminum foil to isolate it, yet keep it handy if needed.

If someone from Tesla is reading this, perhaps it’s worth a software update? This is going to burn lots of customers who may not be as tolerant of this bug as those of us on this forum. It’s a little embarrassing that this has not been fixed, after years of reports.

We dearly love our car, but if it weren’t for the good folks on this forum, there would be a lot more frustration among owners.

 

[Akikiki]

@Phil Stasik, That was an excellent post. Thank you in behalf. I don't have 2020, must ask. You can add/remove the fob on a 2020 S? I thought that started with 2021> Good to know.
I see on your post that you rebooted (#5) after you added it back. I believe it would have cleared the message if you had performed your reboot between #3 and #4.
And I recognize there was a delay before it cleared - hmm about the time you started charging. There are occasional fob firmware updates. All it usually takes is moving the fob near the car - but on later year cars such as yours. So, it might be that the car was delivering a firmware update to the fob before it cleared. Point being, plugging the EV charger in and it started might just be about the time it finished the firmware update.

Back to your post. These posts are very worthwhile and valuable to seasoned owners and new owners alike. We thank you for your contribution.

 

[Phil Stasik]

@Phil Stasik, That was an excellent post. Thank you in behalf. I don't have 2020, must ask. You can add/remove the fob on a 2020 S? I thought that started with 2021> Good to know.
I see on your post that you rebooted (#5) after you added it back. I believe it would have cleared the message if you had performed your reboot between #3 and #4.
And I recognize there was a delay before it cleared - hmm about the time you started charging. There are occasional fob firmware updates. All it usually takes is moving the fob near the car - but on later year cars such as yours. So, it might be that the car was delivering a firmware update to the fob before it cleared. Point being, plugging the EV charger in and it started might just be about the time it finished the firmware update.

Back to your post. These posts are very worthwhile and valuable to seasoned owners and new owners alike. We thank you for your contribution.

Thanks Akikiki!

I did not know that the fobs did firmware updates. It’s really a minor gripe, but I can imagine this infuriating ordinary users.

 

[Akikiki]

Fob firmware updates are rare, and I think most of those times, they go unnoticed because people often put the fob in the cup holder area anyway. (That's where Tesla said the fob should be when getting a firmware update. I am only guessing that's what yours got, because you said you seldom/never use it. So, it was first time or first time in a long time it had been near the car. And that firmware update likely accounts for the delay in something useful going on between deleting it and adding it back. I don't know, but I would guess, it does not need to be assigned to the car to receive an update, just near it.

 

[DABESQ2]

Wow what a thread, harkened back to Better Caul Saul with that FARADAY bag reference. Everyone put a multimeter on your Christmas list, cheap ones are like 5 bucks and a good one is 15-20, then you can test all your batteries and toss the BAD ones and use the good ones. I bet you have all thrown out good batteries at times and tried to use bad ones to much frustration. I take my meter to my girlfriends house and literally toss out half of her 'good' batteries and save at least 30% of her bad batteries in the recycle bin.