Spare key suddenly stopped starting the car?

[storminmike]

The spare key gets used mostly at weekends but for whatever reason it now wont start the car

It does work the door by button/remote both opening and shutting. It does go into the steering column, turn and all the lights come on......but no engine cranking?

I've read about duff batteries but this surely can't be the case if it remotely operates the doors?

I saw a you tube on an older BM about reprogramming a key but before doing anything daft to the daily driver I thought I'd ask first?

Have I missed something?

Mike

[storminmike]

Further to this I found out that if you put the orignal working key in the igintion> Turn on then turn off and put the other in within 3 seconds turn on>turn off it must somehow flash the code back at the other.....and it did

Well it did.....for a while and now it wont work again....and the central locking aint working on this duff key either now. Really frustrating as what I don't want to do is screw the working one

[X5Sport]

Internal battery failure?  The code system should mean that the keys still have valid codes even if not used for months.  It could be that the internal rechargeable battery has given up as it needs using regularly to keep it charged - which might also explain the central locking issue.  If allowed to go dead it will take a while to recharge off the induction ring around the key slot.

[storminmike]

[quote="X5Sport"]
Internal battery failure?  The code system should mean that the keys still have valid codes even if not used for months.  It could be that the internal rechargeable battery has given up as it needs using regularly to keep it charged - which might also explain the central locking issue.  If allowed to go dead it will take a while to recharge off the induction ring around the key slot.
[/quote]

Well experiments so far mean that I have managed to make it start the car....albeit moments later..(EDIT after taking the key out then again trying to start the car)..the handshake is lost. This must mean that the key is capable of being programmed with minimal juice to work again?



In the midst of that I cannot now make it open or close the car either.

Maybe if I get it to start the car I take it to work (30 mins) with the working key with me and that might be enough to re-charge it...if indeed it's a battery issue?

What bothered me was that it did works the doors but not the ignition which you'd think both or neither if charged or dead

[X5Sport]

I would expect both too..... ???  It's possible the car system has 'lost' the key so it needs reprogramming to the car.  The procedure is on here somewhere, but charge the key for a while.

A 30 min charge may at least give you a better chance, but it probably needs several days of such use to get it fully charged.

You can also cut the key open and replace the cell.  Guides on line for doing the surgery.  Cheaper than £100+ for a replacement.

[storminmike]

Well

I followed the "put the working key in", turn on then off (without starting) and quickly throw the duff one into the ignition and repeat. The key was then re inserted and it started, much like yesterday.

I drove for 30 mins to work then stopped. Key out, waited a few seconds then put it back in....it started again...hoorah.  Took it out for around a minute and..................feck all, dead again. Now I'm to sure how long constitues charging the battery up by the EMF field but its not looking good.

I've seen the slice it open videos and the fact that its partially soldered in too. Not certain what the replacement battery type would be though so if anyone knows the type/size/supplier of a know fit that would be great.

Mike

[Rust]

I think the EWS system is passive (no battery required in a valet key) so even if the battery failed in the master key the car will still start.

The EWS system read off the keys rf id chip

I would try getting a valet key (grey one no remote) from a dealer, should cost about £20 I think

hope this is of some help

[storminmike]

[quote="Rust"]
I think the EWS system is passive (no battery required in a valet key) so even if the battery failed in the master key the car will still start.

The EWS system read off the keys rf id chip

I would try getting a valet key (grey one no remote) from a dealer, should cost about £20 I think

hope this is of some help
[/quote]


) ) Might be the red bull but I'm more confused than ever

I can drive/open the car with the one working key I have...the second proper key I have is the one that died that I can't seem to get to work for more than a few seconds. It did work by inserting the working one then swapping to the dodgy one....but not for very long.

The assumption I have is that the dodgy one has no sustainable power within it and that the key swap enabling proves it is matched (which I knew) but cannot work alone for more than a few seconds. It will make all the ignition come one regardless but not turn the engine over

I dont have a valet key and I guess I should but I guess this dodgy key is no more usefull than one of them as it stands

[storminmike]

Sorry to bump

Anyone know the correct battery type to replace please?