Remote key working intermittently

[SamW]

I've been searching some information related to this but have not found the definite answer yet.

So, I got two "diamond" shaped remote keys for my X5, let's call them A and B. When I bought the car, the key A was the main key and it worked just perfectly. The key B however, couldn't be used to open or lock doors remotely.

Then maybe two months into the ownership, the key A started to require a several pushes of buttons to open or lock the doors and it got worse little by little to the point I was almost forced to use the door lock manually to open and lock the doors. I thought the battery was going bad so at this point I got the key A checked by a company specializing in car keys. It turned out the battery was fine, micro switch buttons were fine but the key wasn't sending a signal. They added some solder to the edge of the circuit board and reported that all is fine now. The key A seemed to work a little bit better after this but still required several pushes to operate the lock remotely.

I then got the key B check in order to see if problem is in the car itself or if the key A would be defective in some other way that the shop couldn't test. The key B was tested but its battery and micro switches were also in shape. I then synched the key B with the car and it now works for opening and locking the doors but it still usually requires several pushes of buttons, not so many than initially though. Locking the doors with the button inside the car works fine by the way.

So all this makes me think that there are two options now: either the both keys are someway defective in which the shop couldn't test or the problem is in the car itself. I bet it's the latter, so where should I start looking? I bet there is some kind of a receiver somewhere or maybe the wiring? Anyone faced a similar issue?

[andrewwynn]

Both of my keys acted similarly to your symptoms. Resolved for a couple years with a reflow of most of the solder joints then after a few years of random drops the key I didn't lose on a road trip started doing it again then finally stopped.

I had an even weirder situation: it would work if I slammed the tailgate so I was pretty sure it was wiring or related to the amplifier in the tailgate.

I replaced my key with a new one and once synced it works perfectly. The problem was entirely the key.

I haven't had time to fix the solder in the key yet but that would probably bring the key back to life.

I used an online dealer to get the key enough of a discount that I got a non remote valet key I can leave hidden in the car for emergencies included for the same price as just the key from local dealer.

[SamW]

Okay good to know that the problem could still be in the keys themselves after all. Can't rule out the wiring and amplifier though. As a matter of fact, where is the amplifier located exactly and is there some way to test it? Wiring is in the hinges right? It's just that everything else, the rear lights etc. works fine but I guess it would be possible that it was just the remote control that wouldn't work.

And altogether, the key B now usually works like 75 % of the time while initially the key A was like around 5 % certainty.

[andrewwynn]

Age of keys?

I would follow my lead: get one replacement key from the online dealer save like $50. Use your existing key as a "hide a key".

It will save you hours of snipe hunting.

[Corellian Corvette]

There is a guy online who repairs these pretty cheap (along with EWS modules) - could just be a failing battery since the keys sync but then seem to lose range. I've sent a bunch of keys to him and they all came back working great.

https://www.bmwgm5.com/

[oldskewel]

Just in case this is not already difficult enough ...

Consider that a problem with the central locking system - completely independent of the wireless / remote subsystem - could be causing problems.

Is everything else in your locking system working perfectly? E.g., button in central console - do all door lock actuators reliably and powerfully lock and unlock when commanded? Controlled by door buttons? Do windows control as commanded?

I once had a problem with my 2001 3.0i where a (thankfully not intermittent) electrical problem with my driver's door lock actuator caused flakiness in other parts of the system (including rear door lock actuation) and complete failure of the remote entry functionality. Summarized in a thread on here somewhere. As soon as I swapped back in my mechanically cracked, but electrically good driver's door lock actuator, everything was rock solid - keyless entry, rear door lock actuation, etc.

Whatever you do, make sure your mechanical door key cylinder does not fail and leave you locked out, as they often do when needing increased usage when the remote entry dies or becomes flaky. It seems the key cylinder lasts about a year of daily usage before failing.

If you had not taken your keys to a pro, and if you do not have any other locking control problems, I'd expect the keys to be the issue. But ... now it becomes a question of what kind of testing the pros did, and how much faith you have in anything they did.

Another option that may be helpful for debugging is to buy a remote key / fob on eBay. I bought 3x of used BMW diamond keys when I first got my X5, using them as fobs on keychains with non-remote Genuine BMW keys. It seems those are no longer sold there, but brand new Chinese eBay knockoffs are. Surely the EWS will not work on those (despite claims) but the remote functionality should, and is easy to program following the standard sequence. So as a test, and as a future backup, you could get one of those, program it, and evaluate its reliability. If it is rock solid, then that confirms key flakiness as the problem. If still flaky, it points elsewhere.

[andrewwynn]

Solid advice on the eBay key fob. It's cheaper than replacing the key.

That said new key I would have done the year I bought my car (2015) had I known what I know now.


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[Corellian Corvette]

I have heard horror stories about those eBay key fobs. Just send your originals off to be fixed. You don’t use any other key spot, no programming, and the guy who fixes them tests them. If your key fob can be synced then the EWS is fine. Almost certainly it’s just a aging battery.

[SamW]

Originally Posted by andrewwynn

Age of keys?

As for the age of keys, I’m not really sure but can’t see why they couldn’t even be original from 2003 if that’s possible.

Answer to oldskewel’s message, the central locking itself is working fine. Need to check the door buttons though. And yeah, I’ve noticed that the door lock probably couldn’t take too much of a use but thankfully the key is now working so well that I rarely need to operate it manually. And when it comes to the shop I sent the keys to, they specialize in car keys so I hope they know what they are doing. Never can be sure though. They were able to check that the batterys were fine (I believe they measured them to be 3.0 V), micro switches function and they can also test if the key is sending any signal. According to them, the lack of signal was the problem with the first key but the addition of solder fixed it.

Also interesting point about the key fob. So it would work for opening and locking the doors remotely after just syncing it with the car? It would definitely be a cheaper option to test with that first.

[andrewwynn]

Many people will just add an eBay key as a fob saved like 93% over a whole key. That said my new key was about $160 and worth every penny


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