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Discussion Starter · #1 ·
I had my E46 stored for several years. On my way back to use it, the workshop man (not a BMW specialist) charged with preparing the car tells me that everything is ok, except that the key doesn't seem to function. (It's the newer key model.)

Does the key 'suffer' from an extended storage period, like its battery getting empty (is a 'full' key battery prerequisite for its starting capability), or would it just have to be re-synced? I know that the starter battery was down and had to be exchanged.

Assuming the key is probably the cause, what would be a troubleshooting algorithm that would pinpoint the cause so it can be fixed?
 

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Discussion Starter · #3 ·
As the matter isn't sufficiently clarified at this stage to take decisions, I talked to BMW and received this response (gist of it):

'It could be sufficient to sync immobiliser and key. This could be done with a universal tester. A fully functional key battery is not necessary.'

If this is correct, then I should be able to start the car, also for several days (until this battery has been changed) - right? Where in everyday operations would the 'empty' key battery make itself felt?
 

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Discussion Starter · #5 ·
I appreciate the sense of humour I mean to hear from your response. However I speak a foreign language here and am therefore in a disadvantageous position compared to you and most others (if there are any others). Also, I'm in a nasty situation which I would like to escape from ASAP.

What I meant to say with 'A fully functional key battery is not necessary' is that a key battery not used for a long time will be 'partly functional' only, compared to one which has been used regularly. And that was a question, because I still don't know for sure.

So again, the BMW response (gist of it, translated) was

'It could be sufficient to sync immobiliser and key. This could be done with a universal tester. A fully functional key battery is not necessary.'

And my question then

'If this is correct, then I should be able to start the car, also for several days (until this battery has been changed) - right? Where in everyday operations would the 'empty' key battery make itself felt?'

Care to give it another try?
 

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Discussion Starter · #7 ·
I'm still far away, not on location yet. I'm trying to remotely guide a good mechanic (autoelectrics included, but not BMW specialist) so he can overcome this last-minute problem and finish the job before my arrival. Seeing on YT how fairly complicated it is to open/close this type of key, I'm certain he will try to avoid this part and ask for it to be delegated to someone specialised.

Again, if someone in this forum familiar with this situation just truthfully answers my questions, then this should be all it takes:

- After immobiliser and key have been synced (using a universal tester), the car should start; if it starts once, it will start again: Right or wrong?

- So I should have some time to get a new key battery: Right or wrong? And: Where in everyday operations would the 'empty' key battery make itself felt (if at all)?
 

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I just asked on another forum if the battery needed to be in the FOB to start the car and the answers was NO. So I was wrong - a dead key FOB battery will not prevent starting.

When the mechanic said "the key doesn't seem to function", what exactly does that mean? Does the ignition lock turn but the car doesn't start? Does the ignition lock not turn? Does the car crank but not start?

If the ignition lock turns but the car doesn't even crank, then it sounds like the key is no longer synched to the car (EWS). If the ignition lock doesn't even turn, then the mechanic has the wrong key. If the ignition lock turns and the car cranks but won't start, then it's not the key at fault.
 

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Discussion Starter · #9 ·
Thanks. Without going into details, the 'what exactly happens' path has already been exhausted. Getting the right answers to the questions asked should solve the problem. So could we focus on my questions please?
 

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So could we focus on my questions please?
There are just three possible reasons that I can think of:

1. If the ignition lock turns but the car doesn't even crank, then the key is no longer synched to the car (EWS) provided the vehicle battery is fully charged.
2. If the ignition lock doesn't even turn, the mechanic has the wrong key.
3. If the ignition lock turns and the car cranks but won't start, then it's not the key at fault.
 

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Discussion Starter · #11 ·
Ok. If we exclude 2 and 3, is it true that a car mechanic with a universal tester can sync key and immobiliser, meaning the car will start then? And it will keep on doing so, even if the key battery is down? (It won't stay that way, I'll have it fixed, but it may take a few weeks.)

And what is this battery good for? Where in everyday operations will I feel its down status?
 

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Ok. If we exclude 2 and 3, is it true that a car mechanic with a universal tester can sync key and immobiliser, meaning the car will start then? And it will keep on doing so, even if the key battery is down? (It won't stay that way, I'll have it fixed, but it may take a few weeks.)

And what is this battery good for? Where in everyday operations will I feel its down status?
When I ordered a new key from the dealer, it took a few days to arrive and was already coded for my car via the VIN upon arrival. I doubt a 'run of the mill mechanic' has the needed tool to add a key to the EWS but a BMW mechanic certainly would. Moreover, the EWS can only store 10 coded keys at any one time. If the EWS already has 10 keys stored, one key will need to be deleted from the EWS before another can be added. Once a key is coded in the EWS, it should work always, regardless of the battery status in the key FOB. The battery in your key is for remote locking/unlocking only as I have come to learn.
 
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