Key Fob Low Range

[Lashko]

Greetings to everyone! I have been struggling to resolve an issue on my 2012 BMW M3. I have severely low range on my key fob. I literally have to hold the key fob next to the diversity antenna module that’s under the rear glass for it to unlock/lock the vehicle. I have replaced the diversity antenna module and even took my vehicle to the dealer for them to reprogram a brand new key. I also replaced the amplifier. If anyone has had a similar issue or any insights I would greatly appreciate it.

[Thumbie]

Wow so literally right next to the car?

and it still does it AFTER a new key and new antenna?

My range is closer to 20ft at best, which I felt was short. Curious is anyone has a fix.

[Lashko]

Originally Posted by Thumbie

Wow so literally right next to the car?

and it still does it AFTER a new key and new antenna?

My range is closer to 20ft at best, which I felt was short. Curious is anyone has a fix.

Literally right next to the car! At first I thought it was the key so I replaced that first. Next came the diversity antenna module and then the amplifier right after. It’s so weird. I also had a thought that maybe it’s the battery as the E9X platform is very picky. I also replaced the battery and coded it. Nothing fixed my issue

[askme]

somewhere I saw that leaving the fob on an apple watch charger will fully recharge it and give significantly more range. May not work, but should be easy to find one and drop your key on it for half an hour.

[Lashko]

Originally Posted by askme

somewhere I saw that leaving the fob on an apple watch charger will fully recharge it and give significantly more range. May not work, but should be easy to find one and drop your key on it for half an hour.

I have Comfort Access so there is a replaceable battery. I tried 2 brand new batteries. No results, but thank you for your input.

[KawBoy]

You are doing a lot better than I am. Sometimes I have to open the car with the key. Everything is dead. Checking for errors, nothing shows up. I have tried new batteries, the spare key... nothing works. And sometimes it may take weeks to happen again.

[PYE46M3]

Is the car battery good? I realized one time that my battery had discharged a lot and the fob wouldn't even unlock the door. hooked up the car to my CTEK charger and the fob started working again.

[KawBoy]

Originally Posted by PYE46M3

Is the car battery good? I realized one time that my battery had discharged a lot and the fob wouldn't even unlock the door. hooked up the car to my CTEK charger and the fob started working again.

Yes, battery is good. As a fact of the matter, I replaced a good battery just for the sake of this thing, and nothing.
I do charge my battery every other weekend [CTEK], as my commute is pretty short, but nothing helps.

[dar2008]

I am having the exact same issue on my E92. I have to hold the key around the back window for the fob to work. I don’t have Comfort Access on mine.

I was considering buying a replacement Diversity Antenna until I saw your attempts didn’t fix the issue.

Have you made any further progress on resolving?

[Lashko]

Originally Posted by dar2008

I am having the exact same issue on my E92. I have to hold the key around the back window for the fob to work. I don’t have Comfort Access on mine.

I was considering buying a replacement Diversity Antenna until I saw your attempts didn’t fix the issue.

Have you made any further progress on resolving?

No further progress as of now, but I did notice that my new amplifier is acting up. Gonna be sending it to BavLogic out in Texas for them to take a look at it. That could be the culprit. I once read somewhere that the key fob radio frequencies go through the amplifier. I’m not sure how accurate that is.

[dar2008]

Originally Posted by Lashko

No further progress as of now, but I did notice that my new amplifier is acting up. Gonna be sending it to BavLogic out in Texas for them to take a look at it. That could be the culprit. I once read somewhere that the key fob radio frequencies go through the amplifier. I’m not sure how accurate that is.

Good news for me today. I removed my Diversity Antenna, took it apart and gently cleaned the circuit board where it was a bit cloudy / corroded (see pic), using 96% alcohol.

Put it all back together and voila, it works! I can now lock / unlock the car from up to 20ft away. Very happy I didn’t fork out £100 on a second hand diversity antenna.

I hope you get yours working too.

[Lashko]

Update: I finally figured out my problem. There is a connector that attaches to the rear windshield which connects to the Diversity Antenna Module. I had my rear glass removed to replace my quarter panel and the company that removed it cut that wire so now I have to replace my whole rear windshield just to get my key fob working normally. I tested this theory on my daily driver which is an E90 335d. I unplugged that wire and it had the same issue as my E92 M3, plug it back in and all is normal. Thanks to everyone who reached out to help. Hopefully my problem and solution helps someone out in the future.

[Thumbie]

Problem solved!

Although I was hoping it was something like dar2008 did where we could clean or reset something and it brought our range back to normal lol

[Lashko]

Originally Posted by Thumbie

Problem solved!

Although I was hoping it was something like dar2008 did where we could clean or reset something and it brought our range back to normal lol

If only my problem was as simple as dar2008. Most of the time it ends up being the diversity antenna module, but mine is one of those rare cases. I’m trying to figure out how those little windshield electrical lines work? Are they antennas for the radio frequencies?

[Z K]

Originally Posted by Lashko

If only my problem was as simple as dar2008. Most of the time it ends up being the diversity antenna module, but mine is one of those rare cases. I’m trying to figure out how those little windshield electrical lines work? Are they antennas for the radio frequencies?

They are used as antennas. That's why newer cars don't have the antenna that stick out and up like older cars.

[lofud]

Originally Posted by Lashko

Update: I finally figured out my problem. There is a connector that attaches to the rear windshield which connects to the Diversity Antenna Module. I had my rear glass removed to replace my quarter panel and the company that removed it cut that wire so now I have to replace my whole rear windshield just to get my key fob working normally. I tested this theory on my daily driver which is an E90 335d. I unplugged that wire and it had the same issue as my E92 M3, plug it back in and all is normal. Thanks to everyone who reached out to help. Hopefully my problem and solution helps someone out in the future.

Hi, I have the same problem ona X6.
This plug your talking about is a wire running from the amplifier on the back window to down 1 of the pillars?

I've been chasing this same issue for weeks and searching the net me somehow have only come across this post after weeks of hunting.

[TheStevo1000]

I have the same problem with my key fob only working within a few inches of the antenna. I'm willing to buy a used one to swap out, but does it have to be re-programmed or anything?

[Adam M]

No, it does not to my knowledge.

I swapped my amplifier out to a tv version and after coding the tv in, it just worked - I suppose it’s possible the aerial amplifier was coded but I don’t think so.

I just read this post from the beginning listening to the OP and was about to type, have you checked the connection to the rear screen. He seemed to be replacing every available component but made no mention of the aerial itself, only the amplifier.

If you know it works but you’re having range problems it only going to be the aerial or the power level to the transmitter and receiver.

[yardbro]

Originally Posted by TheStevo1000

I have the same problem with my key fob only working within a few inches of the antenna. I'm willing to buy a used one to swap out, but does it have to be re-programmed or anything?

If you do go this route, the diversity antenna does not need to be programmed when replaced.

[MakeM3sGreatagain]

Both of my key fobs stopped working to unlock and lock the doors. CA doesn't work as well. I have to use the 🔑 to get in Both key fobs will start the car& I checked the fuse and it appears to be fine. The manual door lock and unlock button works as well. I'm out of ideas at this point.

[TheStevo1000]

I could never figure it out, so gave up, gutted my car and turned it into a dedicated track car haha.