Car key problems

[MHarvey82]

Hey. Does anyone know how to fix the keys if they stop getting recognised by the car. Won’t unlock the car without using buttons and the car doesn’t always recognise when inside. I’m struggling to believe the car is the problem as 1 key stopped working properly four months ago and the other the past week. I know not the end of the world but frustrating and it should work! I have a 2016 XC90 and have changed the batteries a couple of times to try and get them to work.

Thanks for any help and advice you can give

[nu11eaf]

The only times I have had a problem with the key fob are if the battery is nearly dead or the fob has been in the same pocket as my phone and the signal has been blocked, simply moving the phone or fob then allows it to work, I did have one instance of a poor battery connection.

[pallison]

Make sure to use good quality batteries, as I replaced one original battery with a no name equivalent and it died after a couple of months. If you have keyless entry the batteries are only expected to last around a year, whereas with previous cars they would last indefinitely.

[MHarvey82]

Just got some Duracell batteries but it hasn’t fixed it. Booked in with Volvo next week. Actually sacred to think what they will try to charge.

[fergus]

Originally Posted by pallison

If you have keyless entry the batteries are only expected to last around a year, whereas with previous cars they would last indefinitely.

That's a bit of a relief. Roughly consistent with my experience. I think battery quality (Duracell / IKEA / whatever) must also have some influence on lifetime?
It seems to take a long time for the death throes to become terminal. I am on my 3rd set of batteries for two keys in just over 2 years. I must learn to fit new, good quality replacements at the first symptoms. Up to now, I have been seeking to extract every last bit of juice from them and it's just too anxiety-inducing. And probably risky.
PS One key gets a lot more use than the other (I mean, a lot) and yet for each key the battery lifetime has been about the same at about 1 year. Maybe they are humming away 24/7/52 scanning for any request, or opportunity, to work? A bit like Bluetooth?

[Paul burns]

I had same problem with cheap batteries, no problems with Duracell. Annoyingly when I first had problems I asked the dealer to look at problem, there response was ‘ we checked the battery and it’s ok showing 1.5 volts ‘. As we or I know you can have 1.5 volts with virtually zero amps, you can’t test these batteries.
I should mention the fault was intermittent and as usual didn’t show itself at the dealership.
As other people said, at first sign of problems replace with new quality battery.

[techwatcher]

Originally Posted by fergus

Maybe they are humming away 24/7/52 scanning for any request, or opportunity, to work? A bit like Bluetooth?

Essentially that is what's happening - the car emits a (short range) radio signal which is received by a key within range so the key has to be listening for the car's radio signal.

However with recent cars the scanning isn't quite continuous. In recent cars I understand that the keys enter a 'sleep' mode after being immobile for a period of time. Nothing to do with improving battery life but a security feature intended to mitigate the threat of the so-called 'relay attack'.

[Whiterdesign]

These keys were only introduced in the last couple of years, they can be identified by the letters MS after the serial number. MS = motion sensor

[OldEngineer]

There is a 'protection' function in the car if a second key is left inside. This second key gets deactivated when the primary key is used.