Fob Buttons Not Working

[phoneticsoft]

So I have no way to lock my car (and be able to unlock it later). None of the key fob buttons work. So far I can confirm:

• key fob is transmitting a signal (used the old AM-radio test)
• checked the diversity antenna/module (underneath the headliner at the back near the rear window. Connections look good but I don't think it's getting power. There are 3 wires going to it...red, black, and blue/red. Can't seem to get 12v with my multimeter from any of those.
• lock/unlock button on the dash works fine
• trunk button in driver's footwell pops the trunk just fine
• when I press any of the fob buttons, I get nothing...no relay click...just dead silence

What fuse or fuses should I be looking at for that circuit?

Also I do *not* have CA Comfort Access or iDrive, if that's helpful.

What else could this be?

[jdog006]

I don't have a fuse schematic handy. But I bet there is a diagram in the user manual. In my 2009 E82 (135i), there is a physical key in the fob that slides out from the bottom for cases of loss of power. I assume you also have one. This will allow you to lock/unlock until you get it worked out.

[phoneticsoft]

Originally Posted by jdog006

I don't have a fuse schematic handy. But I bet there is a diagram in the user manual. In my 2009 E82 (135i), there is a physical key in the fob that slides out from the bottom for cases of loss of power. I assume you also have one. This will allow you to lock/unlock until you get it worked out.

Thank you for the reply. Yes, normally I'd be able to use the physical key but there's a separate issue there. The mechanical linkage in the driver's door is also broken and that won't let me lock/unlock the door using the physical key.

[mkeiser]

Originally Posted by phoneticsoft

• key fob is transmitting a signal (used the old AM-radio test)

I'm the most suspect of this "test". The most common issue would be a dead battery... Open the fob and check battery voltage. Replace if necessary. https://www.e90post.com/forums/showthread.php?t=1469784

I would also be scanning the car to look for any codes stored related to CAS module.

[MParallel]

Sounds like a dead battery to me. Also the signal isn't in the AM band, so I doubt such a test works at all.

You do have a way to lock/unlock as the mechanical key is exactly for this purpose.

[phoneticsoft]

Originally Posted by mkeiser

I'm the most suspect of this "test". The most common issue would be a dead battery... Open the fob and check battery voltage. Replace if necessary. https://www.e90post.com/forums/showthread.php?t=1469784

I would also be scanning the car to look for any codes stored related to CAS module.

Thank you. Yes, replacing the battery in the fob with a brand new one was the first thing I tried....unfortunately didn't help. Mine has the VL2020 battery that has to be soldered in, so it wasn't as simple as just popping in a new CR2032.

I scanned with Bimmerlink and I do see a code from the Professional radio saying it can't see the diversity antenna, which (if I understand correctly) helps with AM/FM reception but also receives the signal from the fob to lock/unlock doors. I don't think my diversity antenna is getting power.

[phoneticsoft]

Originally Posted by MParallel

Sounds like a dead battery to me. Also the signal isn't in the AM band, so I doubt such a test works at all.

You do have a way to lock/unlock as the mechanical key is exactly for this purpose.

Yes, normally I would use the mechanical key but I have a separate issue with the linkage in the driver's door that is currently preventing that option from working. I'm chasing both issues simultaneously but was hoping to get the remote door lock/unlock feature working...I feel like I'm really close.

[mkeiser]

Originally Posted by phoneticsoft

Thank you. Yes, replacing the battery in the fob with a brand new one was the first thing I tried....unfortunately didn't help. Mine has the VL2020 battery that has to be soldered in, so it wasn't as simple as just popping in a new CR2032.

I scanned with Bimmerlink and I do see a code from the Professional radio saying it can't see the diversity antenna, which (if I understand correctly) helps with AM/FM reception but also receives the signal from the fob to lock/unlock doors. I don't think my diversity antenna is getting power.

Thanks for all the additional information. That is very helpful in troubleshooting.
If you can get access to ISTA that should help with some wiring schematics to hunt things down. All I can help with is this forum post, might get you some ideas.
https://www.bimmerforums.co.uk/threa...-cable.587564/

[phoneticsoft]

To close the loop on this (no pun intended), I finally got this issue solved. Basically the diversity antenna wasn't getting power because there's a break in the red wire somewhere between the fuse box and the diversity antenna. Instead of pulling the car apart trying to find the break, I just ran a new wire (with an inline fuse) directly from the battery distribution block in the trunk and spliced it into the red wire going into the connector at the diversity antenna. That was easier than I thought it would be.

That sound of my car locking/unlocking when I press the fob buttons has never sounded so good!

What I learned:
-the diversity antenna is grounded by the two black bolts attaching it to the roof; not the black wire as I had once believed.
-the AM radio trick does work. I tuned the AM radio all the way to its lowest frequency, which is close enough to the frequency on which the fob transmits RF (315MHz I think). I actually touched the fob to the radio while pressing the fob buttons and could hear the resulting distortion in the radio signal.