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      11-10-2018, 10:33 PM   #1
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Key Fob Intermittent

2008 335i with Comfort Access

Starting recently the key fob seems to be working intermittently. I replaced the battery twice but to no avail. It appears to be all buttons on the fob that are affected.

I just did some testing by standing in different spots around the car locking and unlocking it many times in quick succession. It worked maybe 70% of the time, but a couple of times when it wouldn't work it took about 30-45 seconds for it to come right and start working again. Initially I thought it was mainly standing in front of the car that was giving issues but after doing that testing I'm not so sure, it seems now to be randomly anyplace around the car. I only have the one key for it so can't try another.

Any ideas?
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      11-10-2018, 11:37 PM   #2
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It will be harder to get a key when you don't have any.
And you will be more stressed.

Order one from BMW.

keyfob repair
https://www.e90post.com/forums/showthread.php?t=1510527
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https://www.bimmerfest.com/forums/sh...d.php?t=903551
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      11-11-2018, 02:35 PM   #3
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Quote:
Originally Posted by lime View Post
2008 335i with Comfort Access

Starting recently the key fob seems to be working intermittently. I replaced the battery twice but to no avail. It appears to be all buttons on the fob that are affected.

I just did some testing by standing in different spots around the car locking and unlocking it many times in quick succession. It worked maybe 70% of the time, but a couple of times when it wouldn't work it took about 30-45 seconds for it to come right and start working again. Initially I thought it was mainly standing in front of the car that was giving issues but after doing that testing I'm not so sure, it seems now to be randomly anyplace around the car. I only have the one key for it so can't try another.

Any ideas?

I had similar issue back when I first bought the car. Test this and report back, try standing really close to your car, if the remote works %100, and then it stops working as you are moving away from the car then let me know. If that is the case. Then you need to replace the FBD module.

The module is placed at different location depending on your model, I have an E93, the module is in the rear mirror, so I replaced that and my remote has been working perfectly ever since. So let me know and I can help locate where your FBD module is.
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      11-14-2018, 06:13 AM   #4
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Quote:
Originally Posted by nate93 View Post
I had similar issue back when I first bought the car. Test this and report back, try standing really close to your car, if the remote works %100, and then it stops working as you are moving away from the car then let me know. If that is the case. Then you need to replace the FBD module.

The module is placed at different location depending on your model, I have an E93, the module is in the rear mirror, so I replaced that and my remote has been working perfectly ever since. So let me know and I can help locate where your FBD module is.
Thanks for the idea, for about 10 seconds I thought this was the problem, but then it started doing it randomly again from anywhere around the car and any distance. I did note however that if I do big bursts of locking and unlocking it will just stop reacting to any input for 10-30 seconds. Maybe that's a symptom, or more likely just a feature to stop accidental remote commands?

I'm starting to think it might be the remote, but it's hard to test without a spare. Is there any cheap way of testing this? Local price on a spare key is >$600
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      11-15-2018, 10:33 PM   #5
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Quote:
Originally Posted by lime View Post
Thanks for the idea, for about 10 seconds I thought this was the problem, but then it started doing it randomly again from anywhere around the car and any distance. I did note however that if I do big bursts of locking and unlocking it will just stop reacting to any input for 10-30 seconds. Maybe that's a symptom, or more likely just a feature to stop accidental remote commands?

I'm starting to think it might be the remote, but it's hard to test without a spare. Is there any cheap way of testing this? Local price on a spare key is >$600
How familiar are you with INPA? Open INPA, Chassis, Body, Car Access System. In one of the options, it let you test out your FBD read. It will give you a rating of the signal every time to hit your remote.

It is not the keyfob man, they either work or they don't. But the FBD module fails very frequently
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      11-17-2018, 07:17 PM   #6
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Quote:
Originally Posted by nate93 View Post
How familiar are you with INPA? Open INPA, Chassis, Body, Car Access System. In one of the options, it let you test out your FBD read. It will give you a rating of the signal every time to hit your remote.

It is not the keyfob man, they either work or they don't. But the FBD module fails very frequently
Thanks for your help so far. It's been on my list of things to do so today I installed it alongside a couple of other things, I don't really know what I'm doing but I think I managed to figure it out. Here's what it's doing: https://streamable.com/6q6pw . I'm guessing that this shows that the key is sending a signal perfectly fine? If that is indeed the case I suppose I will be replacing the FBD module. Is there a good guide on how to do that somewhere?
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      11-20-2018, 09:52 PM   #7
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So I've had a look at the diversity antenna module so I can buy the appropriate one:

View post on imgur.com


Before I pull the trigger on a replacement does anyone have anything to add? I'm not 100% sure due to the inpa readout I took, but I'm not really qualified to interpret that data. It seems from research that this could be the issue. I'd appreciate any input as to whether I'm wasting time with replacing this module.
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      11-20-2018, 09:58 PM   #8
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electical e90 pdf
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http://www.google.com/url?sa=t&rct=j...85464276,d.cGU
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      11-20-2018, 10:45 PM   #9
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Sorry but I'm not quite sure what you're trying to tell me with those?
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      11-21-2018, 10:30 AM   #10
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Quote:
Originally Posted by lime View Post
So I've had a look at the diversity antenna module so I can buy the appropriate one:

View post on imgur.com


Before I pull the trigger on a replacement does anyone have anything to add? I'm not 100% sure due to the inpa readout I took, but I'm not really qualified to interpret that data. It seems from research that this could be the issue. I'd appreciate any input as to whether I'm wasting time with replacing this module.
I would get on eBay, and find one in there instead of buying it brand new!
INPA only takes you so far, it doesn't really tell you much if FBD is fault.
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      11-21-2018, 02:16 PM   #11
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Quote:
Originally Posted by nate93 View Post
I would get on eBay, and find one in there instead of buying it brand new!
INPA only takes you so far, it doesn't really tell you much if FBD is fault.
Yeah I've got one lined up from a wrecker for $60 NZD which seems good. We're you able to tell anything from what I filmed or is it mostly useless info?
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      11-25-2018, 11:37 PM   #12
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Quote:
Originally Posted by nate93 View Post
I would get on eBay, and find one in there instead of buying it brand new!
INPA only takes you so far, it doesn't really tell you much if FBD is fault.

So I just replaced the diversity antenna (FBD Module) and no dice. Still the exact same behavior as before. Any ideas? Probably worth noting that it has similar issues with the keyless start, the comfort access door sensors seem to be ok (as long as the key is fairly close), but it's usually a 50/50 as to the car starting with the key in my pocket. I'm not really sure if that's related though. Really scratching my brain here.
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      12-04-2018, 01:36 AM   #13
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      12-06-2018, 10:34 AM   #14
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Sorry, didn't read all the posts..... but does this happen everywhere the car is located? I know that if I park near a large radio antenna my comfort access rarely works at all
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      12-06-2018, 01:52 PM   #15
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Quote:
Originally Posted by 90c4 View Post
Sorry, didn't read all the posts..... but does this happen everywhere the car is located? I know that if I park near a large radio antenna my comfort access rarely works at all
Yeah it does, even when I'm way out in the countryside.
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      01-06-2019, 04:23 PM   #16
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      02-17-2019, 01:51 AM   #17
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The key is getting worse now and seems to only work right next to the door handle, the CA is pretty intermittent now as well which wasn't the case before. Does this point to a key issue?
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      04-14-2019, 05:14 PM   #18
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Update: Comfort Access is no longer working on the drivers side, only the passenger side. Even then it seems to only be the pull handle unlock that works, locking with CA doesn't. Also starting recently when using the keyfob the trunk does not lock while the 4 doors do. The trunk lock switch in the glovebox however does lock the trunk. I really don't know what is going on here, if anyone has any ideas I'd love to hear them.
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      06-26-2019, 10:55 PM   #19
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Quote:
Originally Posted by lime View Post
Update: Comfort Access is no longer working on the drivers side, only the passenger side. Even then it seems to only be the pull handle unlock that works, locking with CA doesn't. Also starting recently when using the keyfob the trunk does not lock while the 4 doors do. The trunk lock switch in the glovebox however does lock the trunk. I really don't know what is going on here, if anyone has any ideas I'd love to hear them.
Did you figure this out?
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      07-25-2022, 12:36 AM   #20
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I have a similar fob problem to this thread, with the added weirdnesses...
- I have two fobs. One works perfectly, 100% of the time.
- The other works less and less. However, once it works, or if I open the car through another means, like the physical key, then it works 100% for a time (a day?).

I don't think it is a battery issue, because, once it works, it works 100% even without "charging" it (inserting into slot). It is almost as if the car falls asleep, and can't be woken up by fob2 (although fob1 works). But once it is awake, fob2 is fine, for at least a few hours. Or maybe there is some kind of RF channel mismatch such that fob2 is slightly off frequency, but the car then "widens" its channel acceptance once it is woken up.

Hints appreciated.
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      05-23-2023, 02:52 AM   #21
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Quote:
Originally Posted by jmb85 View Post
Did you figure this out?
Just found this thread again. For anyone interested I had a new non CA key made by a local locksmith and it has worked fine for years. Guess the original CA key was dying for some reason. In the future I might get a new CA key made to test, not that I really miss it though...

UPDATE: A few days later I've been troubleshooting another E90 CA key and discovered that the battery cover wasn't pressing the battery into the pcb contacts enough. The quick fix was to stick some thin card on top of the battery, and that fixed the other key.
I then decided I should try that on the old key from this thread, and voila it's resurrected.
I can't believe I never heard of this before, or thought to try it, I certainly swapped the battery's themselves a few times. It really makes sense when you consider the intermittent symptoms as well.

Last edited by lime; 05-28-2023 at 07:32 PM.. Reason: update
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