Hi All, new here and hoping to get some advice as I am stumped regarding key pairing.
My key #1 stopped working completely - no central locking - but key #2 still worked fine. I tried recharging #1 but still no joy. Tried re-pairing #1 using turn ignition to position 1, hold lock and press unlock 3-times. No joy, would not pair. I also tried running the pairing sequence with the working key and this also did nothing - locks don't cycle at the end of the process to show it has worked. Resorted to spending £176 for a new key at BMW (key #3). This arrived paired to the car as it can start the car (after some fililng and greasing - they initially wanted to charge me for a new ignition barrel), but it doesn't activate the remote locking. They told me to drive around with it and try it once it was charged. I was sceptical - recharged key #3 but still not working for remote access.

Next step was to run some diagnostics following these instructions found here:
https://garagewire.co.uk/news/compan...d-by-opus-ivs/
1. Check that the central locking works by pressing button in the vehicle. THIS WORKS2. Access to the diversity unit is under the boot spoiler to check for water ingress in and around the unit. NO SIGN OF WATER INGRESS, DIVERSITY CIRCUIT BOARD IS PRISTINE.

3. Check the 12 volt supply to the diversity module (E61 pin 1) (E91 pin 6). If you do not have 12v on (E61 pin 1) (E91 pin 6) we have to suspect broken wires in the right hand hinge loom. All wiring repairs will involve disconnecting the right hand loom and pulling it in through to the boot area via the right hand roof speaker. 12V OK.

4. Check the signal line at the diversity module with the connector plugged in (E61 pin 2) (E91 pin 3). With a multimeter, check for 4.8v on that line then press the unlock or lock button on the remote fob. The multimeter voltage should now fluctuate to show the message is being sent to the CAS module. You could use an LED test probe and watch for the LED flashing when the unlock and lock buttons are pressed. If there is a signal fluctuation or LED flash it suggests the diversity unit is working. VOLTAGE ON PIN2 BUT LOWER THAN RECOMMENDED 4.8V, BUT I HAVE A CHEAP MULTIMETER. ALL 3 KEYS GIVE A DIP IN VOLTAGE WHEN A BUTTON PRESSED - SO DIVERSITY MODULE RECEIVING SIGNALS AND PASSING ON TO CAS.

5. Gain access to the CAS and check for the same signal change at pin 33. If there is a signal fluctuation or LED flash at pin 33 it suggests the diversity unit and the signal line are ok and the CAS is the issue. If you have 4.8v at (E61 pin 2) (E91 pin 3) but do not get a signal change it could be the key or diversity unit at fault. Repeat signal testing using a donor key, as long as it is the same style of key it will generate a signal fluctuation/LED flash. If with the donor key you get a signal fluctuation or LED flash then the customer will need a new key. If not then the diversity unit is at fault. If you do not have 4.8v present on (E61 pin 2) (E91 pin 3) it indicates a faulty/broken wire. Check continuity between pin 33 at CAS to (E61 pin 2) (E91 pin 3). I CAN'T ACCESS THE CAS AND CHECK CONTINUITY, BUT THIS LINE MUST BE OK AS KEY #2 WORKS.

At this point I am a bit stumped. Spent the weekend checking the wiring loom through the glass hatch into the roof on RHS of Diversity module. Found one broken ground wire (brown) and plenty of cracked wires. Replaced all wires leading to Diversity antenna and reassembled. Burnt out fuse #77 at some point in the process, but after fixing this key #2 works as normal, keys #1 and #3 as before: pairing still fails.

I haven't found any threads/info that can explain this. Key #3 is a paradox as I know from key #2 that central locking works, but it doesn't work with key #3 even though #3 is paired with the car - it starts the engine. BMW Dealer did confirm that keys are correctly registered in CAS and none are blocked.
So, is pairing for remote central locking different from key registration in CAS? Is the remote key pairing handled by Diversity module or CAS?? Seems like I will have to try replacing one of these.
Any ideas?

 

Update
So I dropped £250 on a new diversity antenna in a bid to get the central locking working on all keys. Fitted it this weekend, but no joy, none of the keys will pair with the car.
The new diversity unit worked immediately with key #2, I thought it might have to be re-paired with the new unit, which suggests the diversity does not handle the pairing, it just passes the signal to the CAS. But since key #3 must be registered with the CAS to start the car, WHY DOESN'T IT UNLOCK THE CENTRAL LOCKING??!!

 

I had a similar issue that resulted in me having to break one of my rear windows to gain access to the car (the key stopped working while I was on a camping trip and I didn't know that the mechanical door lock cylinder was jammed because I'd just purchased the car). I took the car to BMW and they claimed I just needed a new key, so I begrudgingly bought one for $480. Of course, it didn't fix the issue. Now, I'm not quite sure how BMW ended up solving the problem (they ultimately did the diagnosis for free and charged $171 for the "repair"), but I recall it being something along the lines of having too many keys stored in the system. I'm not sure how that would have happened in my case, but both the new key and the old key started working again after they cleared the extra key memories out. Sorry for the vague description, but unfortunately I won't be able to check the service records for a couple months to find the exact repair description. Anyway, your issue sounds like it could be similar. I had to use the mechanical key blade to lock/unlock the car for a few months before the issue was finally fixed–very frustrating!

 

Thanks. Just after I got the key and it wouldn't pair the dealer did take a look at the diagnostics and told me that key was correctly registered and not blocked. They fobbed me off saying the key probably wasn't charged, which was complete BS. I don't really want to go back to them, I just think it will cost ££ and they won't solve it.

 

It doesn't seem like they know what they are doing. Either guessing around or leading you along at your expense.