Diversity Antennae - Does it control locking/key fob?

[Simm0nS777]

Hey all! 2017 750Li. I had an issue where both of my key fobs ranges got severely diminished out of nowhere. I have to be within a couple feet to lock/unlock. Car usually won't start with key in pocket, but sometimes will. I often get the "Key fob not detected, hold to steering column" error. So it's still reading the fobs, just at super short range. Comfort Access also doesn't work. It also seems to detect the key better the longer it's close by. So if I sit in the car for a minute or two before I leave, it's more likely to start up with the key in my pocket.

I tried the easy things. Replace fob batteries (multiple times). Replace main car battery. Tested fuse continuity etc. Then I took it into a BMW dealer/shop. I also took it to an independent. Neither could find a solution. BMW said if they had to guess they'd say the Body Domain Control Module is bad.

I've read on here that it could possibly be the Diversity Antennae. I mentioned this to them, and they dismissed it as the culprit as they said that is for things like the radio etc. and not really the fobs and fob range.

One thing I've noticed over time, is if I hold the keys towards the back seats, the car will start every time. Also, it will unlock from a further distance if I am at the back of the car. So it can read the key better from the rear.

From what I've seen, the diversity antennae is at the rear of the car. So my thinking is that maybe that is the culprit, even though the BMW shop and independent don't seem to think that would be it. I guess my question is, are they correct and to focus more on the BDC module/something else? Or are they both wrong and it could possibly be the diversity antennae?

Thanks!

[No one]

No, it's not what you think and yes, it's there in the rear (your model is different but probably not that much): https://f20.1addicts.com/forums/show....php?t=2177914. DomMuc (a.k.a. DimMak ) knows!

[Simm0nS777]

Originally Posted by No one

No, it's not what you think and yes, it's there in the rear (your model is different but probably not that much): https://f20.1addicts.com/forums/show....php?t=2177914. DomMuc (a.k.a. DimMak ) knows!

Thanks for the reply! Hopefully DomMuc Is willing to weigh in a bit.

By "not what I think" then are you implying you don't believe it's the diversity antennae?

Thanks again!

[thebmw]

Hmm...I thought the diversity antenna picked up signals from the left and the right (of the car), all types of content, and would be available for cars in all colors, shapes, and sizes. But ironically, it is narrow in its scope.

[Maxx Power]

This is a common issue on the G30 when the TCM battery goes flat. I presume it is the same on the 7 series.

A new battery costs less than $100 from the dealer, and takes about 20 minutes to replace.

Lots of guides on here, or youtube, showing how to change it.
(it is the battery under the antenna)

[No one]

Originally Posted by Simm0nS777

By "not what I think" then are you implying you don't believe it's the diversity antennae?

Exactly. Just as everybody told you.

[Simm0nS777]

Originally Posted by No one

Exactly. Just as everybody told you.

Okay then….thanks for your “help” I guess.

[DomMuc]

Die you already replace th Keyfob batteries? That is I would start with …
Keyfob Antenne (diversity) would be th next ( was offen the culprit on f56/f30 )

[raspbrypi]

Originally Posted by Simm0nS777

Hey all! 2017 750Li. I had an issue where both of my key fobs ranges got severely diminished out of nowhere. I have to be within a couple feet to lock/unlock. Car usually won't start with key in pocket, but sometimes will. I often get the "Key fob not detected, hold to steering column" error. So it's still reading the fobs, just at super short range. Comfort Access also doesn't work. It also seems to detect the key better the longer it's close by. So if I sit in the car for a minute or two before I leave, it's more likely to start up with the key in my pocket.

I tried the easy things. Replace fob batteries (multiple times). Replace main car battery. Tested fuse continuity etc. Then I took it into a BMW dealer/shop. I also took it to an independent. Neither could find a solution. BMW said if they had to guess they'd say the Body Domain Control Module is bad.

I've read on here that it could possibly be the Diversity Antennae. I mentioned this to them, and they dismissed it as the culprit as they said that is for things like the radio etc. and not really the fobs and fob range.

One thing I've noticed over time, is if I hold the keys towards the back seats, the car will start every time. Also, it will unlock from a further distance if I am at the back of the car. So it can read the key better from the rear.

From what I've seen, the diversity antennae is at the rear of the car. So my thinking is that maybe that is the culprit, even though the BMW shop and independent don't seem to think that would be it. I guess my question is, are they correct and to focus more on [...]

did you ever solve your issue? did you inspect/replace your diversity antenna? same issue on my 2014 335i…