I was completely befuddled. How can I have a dead battery in BOTH my keys despite the complete opposite use?!

BHPian ashishk29 recently shared this with other enthusiasts.

About 3 days back, I noticed that my usual key fob didn't work by using the request sensor on the door, but unlocked fine using the buttons on the fob. I didn't think it was a big deal.

A day later, even that didn't work anymore. I had to unlock the car using the physical key within the fob, and of course that set off the alarm

Why? If it's an authorised key, the alarm shouldn't be based off of how the car was locked the last time around. (For the benefit of any who were unaware of this as I was, the car will sound the alarm if you don't use the same method to unlock as the last lock. So if I lock using the fob, and then unlock using the same physical key, it fires the alarm)

So now I had to get in the car, hold the fob at the start/stop button to get it on. Ok. So far so good. Car started fine. And then it kept beeping for "Key not in car" for the next several minutes. I stop at a signal, power the car off, and then on again, and this warning goes away. (WHY?!)

I reach my office, come back to the parking an hour later, and somehow the damn fob works?! HOW?! And somehow in the evening, the fob doesn't work again. Surprise surprise.

All is fine, I come back home, and my first assumption was, yeah, fob battery must've died. So I went inside my home, got my spare fob, which was unused for the last 2 years by the way! And whaddaya know. Same problem even with THIS key.

I was completely befuddled. How can I have a dead battery in BOTH my keys despite the complete opposite use?! I was almost convinced there was something wrong with my car.

Took it down to the showroom, and of course the service assistant suggests the first thing to try, change the fob batteries. "Anyway workshop will ask for the same thing" he says. Fair enough.

At first he changed the battery in one fob. And whadday know, it worked. I asked him to get in the car and fire it up to confirm. He does that, then powers off. However, as he was doing this, I accidentally clicked the button on the other fob which was in my hand, which did NOT have its battery replaced. And it worked?! (Again, WHY?!)

Anyway, he replaced the battery in the second fob as well, and so far things have been ok.

But this raises several concerns for me:

1. Why did the fobs work intermittently for some time?
2. WHY this stupid notion that a physical key unlock will sound the alarm? They have RFID chips inside the keys, can't the damn car detect it's a valid key?!
3. Why can't the car warn me when the fob battery is running low? I talked to a couple of my colleagues, and they said their car cluster warns them of low fob battery. In start/stop type cars, this needs to be mandatory.
4. I am still not convinced that somehow BOTH my fobs were dead at the same time.

Apart from this, got the ECU/EMS updated flashed at the same place. 15 minutes job, I was in and out before I knew it.

Does anyone know what this update was supposed to do/fix? A change-log of sorts?

Here's what BHPian subramanyam84 had to say on the matter:

1. That is simply how the cell electrochemistry works. It simply has caught you at a wrong threshold, where the cell voltage is at the borderline between 'good' and 'bad' for the fob transmitter to work. So it has appeared mystical to you. The discharge curve is not a smooth straight line. But a jagged line over 10's of millivolts. This would happen for a couple of days and the fobs stop working altogether. (I've noticed this pattern of cell death in Honda City, Wagon R, Ford Ikon. Of course there the keys were only to lock/unlock).

2. That goes down to the circuitry. Mechanical intrusion is seen as a mechanical intrusion. I'm not saying it's an intelligent way of addressing the issue. It's just a cheap way I guess. But even if a system were there to detect the original key, your cell was dead, so there's no way of telling. Maybe I should experiment with mine and check, one early morning

3. I'm surprised that the car didn't warn you. Hope someone from Mahindra reads this!

4. You could find literature that talks about constant drain (spare key fob) killing the primary cell faster than a similar primary cell subjected to the same constant drain with occasional discharge spikes (main key fob). It's not intuitive but you've to go into the working of a lithium primary cell to understand this phenomenon. Bottom-line, it's completely normal.

BHPian ashishk29 had the following update to share on the matter:

Update on my key fob situation:

One of the key fobs started giving a weak response today itself.

For reference, I got the battery in both fobs replaced on Dec 22/23. So it's been hardly 2 weeks.

I would've suspected a vehicle issue, but then why did it work for the last 2 weeks?

I am yet to try out the second key with the new battery, but I suspect it'll behave the same.

Read BHPian comments for more insights and information.

I went to the service centre where the service advisor blindly said that the key had to be replaced and that would cost around Rs 5,000.

BHPian ezhil0707 recently shared this with other enthusiasts.

I own a 2016 Honda City iVTEC V MT. I am super happy with the ownership experience so far. I never faced a technical issue in 7 years until the day I found my keys to keep the red light frozen and didn’t lock/unlock the doors.

I assumed it’s the battery which has aged 7 years since the date of purchase. I visited the nearest A.S.S in Coimbatore and as expected the SA blindly said that my key had to be replaced which is around 5k or I had the option to use my spare key.

I decided to fix this issue myself experimenting by going through a lot of forums and YT videos.

Things I purchased include a set of precision screwdrivers (you need a +1.5x25mm size for most of the keys) with a pry tool (FYI: the SA opened my keys with a screwdriver and a coin and damaged the plastic and the alignment. I wonder how A.S.S doesn’t equip them with these minor tools).

I strongly recommend using a prying tool to save your key’s plastic alignment. I opened my key fob and I wanted to try my first luck which is WD-40 spray which will help in cleaning the contacts on the board, if at all present which was posted in many of the videos/forums.

So I tried to take out the board and sprayed a very minimum quantity, cleaned the surface and allowed it to dry for a day. I reassembled it and to my surprise, I got my key back in action.

I am really not sure of what fixed this, but sharing the experience of how investing in a set of tools which cost me roughly Rs 400 Rs for a set of precision screwdrivers and a pry tool can save you with a blind key replacement of 5k.

Is there anybody who has faced this issue and can someone educate us on this with exact data pointers?

Thanks in Advance.

Here's what BHPian Jeroen had to say about the matter:

There are a couple of things that can fail on a FOB and do so.

Obviously, the first one is the battery, it runs out and just requires replacing. Make sure the battery fits snugly onto the two contacts. One underneath, one on the side.

The second problem can be the failure of the microswitches. Sometimes just dirt and then a good cleaning with a good electro cleaner might do the trick.

Sometimes the microswitches are actually broken. They can be replaced, but you need to find a good replacement.

It is very rare for the actual electronic components to go bad. I have seen one case where some of the soldering was done poorly and came undone.

When cleaning the electrical bits off, it is best to use a proper electro cleaner. WD40 is fine as is not conductive, but it will leave some sticky residue behind.

Whereas fixing a FOB tends to be relatively easy, reprogramming it might not. The more fancy the car, the more complex the reprogramming procedure will be, sometimes requiring special equipment.

Check your owner's manual. Replacing the FOB battery should be described, including on how to open the FOB. It will also state if any reprogramming needs to be done.

Here you see me fixing my Jeep’s FOB very similar to how you did yours.

Here's what BHPian KHegde had to say about the matter:

As Jeroen has pointed out, one of the reasons for a FOB Key not functioning could be the requirement of a battery replacement. You would need to refer to your car's owner's manual for detailed instructions.

I can vouch for the above from personal experience. I have replaced the key FOB batteries twice on our 2013 Global Ford Fiesta which came with only 1 key FOB and 1 regular key and once on our 2019 Maruti Suzuki Ertiga for both key FOBs.

Here's what BHPian arnieshwartz had to say about the matter:

We encountered the exact same problem with the key fob for the 2017 Honda WRV (has the same key as in the original post).

Opened it up, cleaned the circuit board generously using rubbing alcohol and Q-tips and even changed the battery for good measure. Put it all back together and it started working okay again.

I'm not sure what caused it to stop working in the first place. The original battery wasn't exactly weak when checked using a multi-meter so it must've been something else that thankfully went away.

I even saw a YouTube video that involved shorting some IC pins but without any mention of exactly which pins. Needless to say, I did not have to try that method.

Check out BHPian comments for more insights and information.

If the original key is already inside the vehicle, is it safe to lock/unlock the car from the outside using the spare key?

BHPian abirnale recently shared this with other enthusiasts.

How does Remote Locking on keyfobs work in XUV7OO?

On our XUV Owners group, there was chatter about a friend leaving his car spare key in the car and was hesitant to lock it thinking it might screw up the security system. So the debate and discussions started. Another owner shared this clip on the group.

Owning to the curiosity in many of us, I decided to do a small experiment knowing what I already knew (I wish we could develop the habit of reading user manuals in more detail!): two simple video recordings of how the XUV7OO AX7L keyfob behaves in some specific scenarios.

XUV7OO AX7L Remote keyfob behaviour video

And specifically the boot, similar to the insta reel above without build-up though.

XUV7OO AX7L - Remote keyfob and Hatch Door Lock/Unlock video

I am about to do one more experiment - leave the keyfob inside the car and use Adrenox Remote function to lock or unlock! If that works, I can simply be moving around with just the phone (and there is a wearable app on Apple Watch)!

So in summary

• The car will not automatically lock you out if you forget the key in the car while taking out stuff from the boot!
• You can of course leave the spare key inside the car and it shall stay deactivated until the car is unlocked with the same key that was used for locking.
• There is no change in behaviour if you use the request sensor on the driver's door handle or the buttons on the keyfob.

Also remember - the safer way to use the key is to leave it in your trousers zipped pocket so you never leave it anywhere, not even inside the car! It should just technically stay with you all the time if you are the one driving car around. And of course, as a best practice, use request sensors (7OO has it only on the driver door as opposed to XUV5OO on both front doors) instead of keyfob buttons to avoid any frequency scanners etc. Not an easy hack but still, why take chances?

Another Saturday lake hopping

And all of this, we were doing while driving around outskirts of the south Bangalore. Bunch of opportunities to click birds, gorgeous sunrise and of course the Red Sparkle!

Here are some pictures:

And here we stand at 32,000 Kms on the odometer. Happy 2023 folks! Stay tuned for more updates.

Check out BHPian comments for more insights and information.

I was asked to bring in both keys with the problem said to take 2 hours to fix.

BHPian VNair originally posted:

This might be a coincidence as I came across this thread the same day I replaced the battery (CR2032) of my keyfob. I own a Hyundai Alcazar and the battery only lasted for a year! However, the battery in my Venue is still going strong for the past 2.5 years.

BHPian raj4466 replied to the post, sharing this with other enthusiasts.

The key fob of my Kia Sonet was giving the battery a low warning in a year's time, asked the service advisor to replace it along with the service. It is then the service advisor informed me that there is a silent recall by Kia as some of the fobs are faulty and will drain the battery, they will be changing the board inside the fob FOC.

But for that I was supposed to bring in both the keys and the process will take around 2 hours as they need to raise a request to the manufacturer and they have to provide a pin to be programmed onto the fob. Please check with your dealer too as Hyundai being a sister concern might be sourcing from the same source.

Kia owners who are facing the issue of key fob battery drain please contact your dealer as it is not a mass recall and they will be doing it for people who raise a complaint on the battery drain issue of the key fob. I will update once I get it done, hopefully by this Saturday.

Check out BHPian comments for more insights and information.

Expiry date on key fob batteries are exceptionally well calculated. It will be better if you change the battery proactively, if it is reaching the expiry date.

BHPian MT_Hyderabad recently shared this with other enthusiasts.

Having the right spare battery for your key fob is critical for peace of mind on long drives.

I faced a similar challenge recently and realized the importance of checking the battery health.

My Tata Safari Dicor comes with 27A battery type.

I bought 5 batteries and changed both the key fob batteries in 2019, the expiry date mentioned on the battery was July 2022, which I didn't memorize by heart (mistake).

Few days back, the battery on my main key fob died and I started using the spare one(which is used only by car cleaner on weekends), unfortunately, it also died within two days. I replaced both the batteries with new ones from the set bought in 2019. I then noticed that the expiry itself is July 2022.

I immediately ordered a new set as the led on one of my key fob was showing low intensity, even with this new cell. I started carrying both the key fob and the remaining one unopened cell everywhere in my laptop bag. Not surprisingly, one key fob died within one day. I was lucky that there was still some charge left in the other.

Today, I received a new set and changed both the key fob batteries together. I didn't bother to test the untouched one from the previous set.

Learnings: Expiry date on key fob batteries are exceptionally well calculated. Please keep a tab on it.

It will be better if you change the battery proactively, if it is reaching the expiry date. The spare battery may die at the same time, even if it is an unused sealed-pack.

May I request everyone to mention what battery type their key fob comes with, and how long it lasted? This may help other BHPians.

Car: Tata Safari Dicor

Battery type: 27A

Years lasted: Full 3 years; till the expiry date mentioned on the battery.

Here's what BHPian Sushil Pingua had to say on the matter:

My car: Honda BRV MT Petrol, 2017 model.

My keyfob uses the CR2032 Button Cells.

The original batteries which came as OEM lasted for around 2 years. After that the batteries were replaced from the Honda authorised workshop and they lasted just over an year. So I decided to purchase these batteries from Amazon/flipkart which last around a year too.

I keep reserve pair of spare batteries in the car.

Here's what BHPian lapis_lazuli had to say on the matter:

Both my car key-fobs have CR2032 cells. The Punto key-fob is still on its original cell and it has been 10+ years.

The Superb remote needed change after about 1.5 years. Both the key fobs.

The cell pictures that OP has posted, I have seen them being used in home security remotes only. A learning for me.

Here's what BHPian Agarwal_Aayush had to say on the matter:

Both my car keys use CR-2032 button cells.

Interestingly, the one I use regularly is still working without any signs of low battery (5 years and continuing), whereas the spare one was dead and had to replace the cell after 2 years, I chose Duracell this time, original came with Panasonic make.

I now use them alternating on a monthly basis.

Car: MS Baleno 2017 make.

Here's what BHPian chillingmonk had to say on the matter:

I didn’t know key fob batteries have well-calculated expiry dates. I will sure go and check now for my 11 year old Hyundai i10 and 8 months old Jeep Compass.

I have been using the same key fob on my i10 since day 1, only for locking and unlocking the doors, and have never had to replace the battery. I thought that once this keyfob runs out of battery, the other’s life will start. Now I know how stupid that sounds. Having said that, since the ignition key on this key fob is our old fashioned, non-nonsense metal buddy, running out of battery suddenly will lead to a half sigh and a full shrug at best.

I can’t say the same about my modern Compass key fob. My jeep comes to life only with its beloved within touching distance, every single time. So, right away, I am going to check the expiry date of its batteries, and its hitherto unused twin. And I’ll probably keep the twin handy in some way, rather than safeguarding it with the full might of my closet.

Here's what BHPian IP_Man had to say on the matter:

My story.

Battery for my main key fob lasted for four years. I did not bothered much about it because I have spare key fob and I was under impression that car can be unlocked manually by dead battery in key fob because ECU can read RFID tag as it is passive.

One day, battery died. I tried to unlock car manually. Suddenly car started honking loudly and all turn indicator started flashing. It was embarrassing situation because everybody around me started looking at me suspiciously. Fortunately I was in my society, my wife brought spare key fob to rescue me from the situation.

Moral of the story, keep battery in the key fob updated.

Here's what BHPian Transmission had  to say on the matter:

Just wanted to highlight that the expiry date on the battery is for quality control purposes (and even then not exactly a hard date like the expiry date, say on a regular plastic milk packet) - and does not depend on the usage - in fact it assumes 0 usage.

In other words your key fob battery will last longer or shorter depending on how much you use it - the expiry date on the battery has not much to do with it once you start using it. Of course, chances are that it will not last that long - provided the original dates were accurate. If you are more interested, you should look into the standby current of the keyfob and the capacity and the self-discharge rates of the specific battery it uses.

Check out BHPian comments for more insights and information.

All Toyota models from 2018 and newer will have to make use of the subscription to continue using the functionality.

According to media reports, all Toyota models from 2018 onwards will need a subscription to use the key fob's remote start functionality. Reports suggest that Toyota offers a range of connected services when purchasing a new model - one of them is the 'Remote Connect' which allows owners to start their cars using their key fobs.

While there is a free trial period, the 'Remote Connect' plan is interlinked with other connected and audio service packages as well. Post the free trial period, Toyota owners will have to shell out either US$8 / month or US$80 / year for the continued usage of the remote start function.

Source: TheDrive