Key tag with replaced battery doesn't open the tailgate with foot movement

[ropetko]

I was able to replace the (non-replaceable) battery in the key tag recently. I know that's not advisable and that I should take the key tag to Volvo dealer, but c'mon! Some brands have the battery charger in the centre console for such key pads, while Volvo just want us to spend the significant amount of money every 3-4 years, no matter if you were using the key pad or not.
The guy in the car key repairmen shop was able to change the battery and I've tried to open the doors with the key tag to test and everything worked well. The car goes well, I'm able to open and close the doors, there's no "Low battery" message at the central console and my key tag is back in the game
However, I noticed that I'm not able to open the tailgate with foot movement. At first I thought the sensor was dirty, but after a couple of days I figured out that if I'm using regular key (different jacket, different key in the pocket) then I'm able to open the tailgate with the foot movement, but not if I'm using key tag. But when I have the key tag, I can open the tailgate regularly, by pressing the rubber plate. I can also fully lock the tailgate and the car by pressing the "close and lock" button on the tailgate, while having the key tag, but IF the tailgate was open by pressing the rubber plate. But, if I open the tailgate from the instrument panel, while the car has been started and driven using key pad, then I'm not able to close and lock. There's a beeping sound, like if you are trying to close the tailgate and lock if the key is out of range. Did anyone experienced such issues? Is there any way to "tell" the system the key pad is authorised to open the tailgate by foot movement?

TL;DR: Replaced the battery in key pad and now I'm not able to open the tailgate with foot movement while using key pad, but am able to open the tailgate using rubber plate. Opening with foot movement also works when using regular key.

[Deleted User 3629]

Guess that's why its advisable that you should take the key tag to a Volvo dealer and not a " car key repairman shop" - pretty sure a Volvo dealer would sort it for you though, at a small fee perhaps

[eugen61]

Guess that's why its advisable that you should take the key tag to a Volvo dealer and not a " car key repairman shop" - pretty sure a Volvo dealer would sort it for you though, at a small fee perhaps

Small indeed, £300 for a new key tag

[eugen61]

I use only the key tag, now is 2 years old and I start to have issues opening the boot with foot movement while still not getting a low battery warning. Sometimes the only way I can open the boot with foot movement is by having the key tag in my trousers front pocket and staying very close to the boot.

So maybe the new battery that was placed in the key tag is not as powerful as the original one was. Since everything else works for you (door opening/closing and engine start) I can’t think on anything else. Make also sure the key is not cold, low temperature could also affect battery power.

[Deleted User 3629]

Maybe this is wrong info - but are you not supposed to use the key-fob - you know, the one that has the easily replacement round cell battery - I'v replaced many of those, takes 2-mins and costs approx 3-4 pounds for two???

[JFDIT]

The key tag is waterproof which is why they say battery cannot be replaced. The battery is the same as the usual remote except contacts are spot welded. Maybe unit has been damaged when taken apart?

[eugen61]

There’s a single frequency generated in the key tag, so if damaged it would not open/close doors and start engine. The signal is quite weak compared to the key fob, I noticed the key tag would not foot open the tailgate when being placed close to my mobile, keys or coins.

I think the issue is low voltage, the new battery could have been affected by heat generated during spot welding.

[ropetko]

There’s a single frequency generated in the key tag, so if damaged it would not open/close doors and start engine. The signal is quite weak compared to the key fob, I noticed the key tag would not foot open the tailgate when being placed close to my mobile, keys or coins.

I think the issue is low voltage, the new battery could have been affected by heat generated during spot welding.

Thanks Eugene, that might be the issue! Although I'm pretty sure I was able to open the tailgate a couple of times and the battery has been replaced some two weeks ago. Maybe it was damaged while opening, but I'm surely not getting and low battery warning. In fact, just yesterday and today I was on a business trip and had only the key tag with me in my trousers front pocket. Could open all the doors and start the engine, it was only the tailgate that wouldn't open nor shut and lock.

Well, the thing is that the replacement cost me some 30 GBP, while Volvo dealer asked some 300 for the full replacement. Since they would have drop the key tag into the trash and issue me a new one, for the 1/10th of the price at least I could try if that works. The guy that owns a legit car keys repairment shop said he wouldn't charge anything if the key tag wouldn't work after the battery replacement

[eugen61]

I used my 2 years old key fob and it would not allow to open the tailgate with foot movement. I was able to open the doors, start the engine, didn’t get any low key battery message. Decided to change the CR2032 battery with a brand new one and opening the tailgate with my foot works again flawlessly. So I strongly believe the problem with your replaced battery key tag is low power due to heat damage to battery during spot welding. I wonder if it would be possible to fix a new battery in the key tag with a “cold” method, not spot welding.

[richyd2000]

New set of Keys (that’s the two main ones and the fob key) for £120 fitted! I broke one of the main keys changing the battery and the fob keys battery was flat also which I couldn’t replace. Anyway, if you go into the main Volvo website and then go to XC40 All Accessories they offer all 3 keys for only £120 fitted. It’s part code 31652473. If you run a pre-Nov ‘19 XC40 the keys have updated software. Mines booked in for a cpl weeks time, bargain!!