[anchovyslayer]

Hi all, I have been experiencing a complete failure of the comfort access feature in my car for the last year or so. The BMW dealership completed an oil change and as courtesy took a quick look at the issue without doing a total diagnostics (attached).

The issue returned an error code for 'Driver Line Disconnected' (see attached printout from dealership), according to their scan tool, all other aerials tested 'OK', only one returned a fault was for the driver side aerial. I figured its either a wire issue, door handle or antenna on the driver side located under the driver side bumper.

So far this is what I've done:
- I found a 'chewed up' Comfort Access wire leading to the driver side antenna and repaired it
- Replaced driver side handle
- Replaced driver side antenna

After all of this, the comfort access is still not working anywhere I am not sure what else to check or do. The key FOB battery is new, iDrive intermittently shows CA limited warning and key FOB works for locking / unlocking the car.

If the passenger side antenna is broken or wires are damaged on that side - could it possibly affect CA functionality every else? as a next step, I was thinking to remove the passenger side bumper in case an animal chewed up the wire on that side as well / needing repair. Also, according to the dealership the CA doesn't have a dedicated fuse, is this possible or if so what is the fuse number?


I appreciate any assistance or guidance for the next steps

[mrpingu]

Did you clear the error after connecting the antenna, is the error not present anymore?

The door handles have their own Fuse, that is fuse 13(7.5A)which is on the FEM module.
Double check the resistance on the aerial to make sure it’s not the aerial itself, you can do this at the FEM-side so you know the signal is reaching the FEM.

I’ts pin 9 and 27 on A173*9B


Edit: also a missing antenna would show the 'comfort access limited function' warning while a missing doorhandle would not give a message at all, there is no check on doorhandle function in place.
I am retrofitting comfort access on my F48 and I haven't connected all doorhandles and no message is popping up, but as soon as I disconnect one antenna I get the warning on the dash / infotainment system.

[anchovyslayer]

Hi there, yes, I did clear the error codes and it came right back.

When repairing the wire feeding the driver side antenna, the original wire size is a 20/22 gauge and after cutting the damaged piece out I replaced it with a 18 gauge - could that be the cause of the issue? should I go back in put on the exact wire size or is that not the likely cause?

As a next step, I was thinking to check the fuse in the FEM as you suggested -- what is throwing me off however, is when I called the BMW dealership, they said there is no dedicated fuse that powers CA

Also, while before I wouldn't get any specific errors in the iDrive system, now I do get a Comfort Access Limited error every time I start the car, see attached.

[anchovyslayer]

Hello again, I checked and replaced the fuses, none of them were blown, but interestingly the prongs connecting to those 7.6amp fuses (there were 3 total) were brown / burnt looking. No other faults are found in the car except for CA, so I suspect its not FEM failure, rather the cord I use for the repair perhaps?

[mrpingu]

Originally Posted by anchovyslayer

Hi there, yes, I did clear the error codes and it came right back.

When repairing the wire feeding the driver side antenna, the original wire size is a 20/22 gauge and after cutting the damaged piece out I replaced it with a 18 gauge - could that be the cause of the issue? should I go back in put on the exact wire size or is that not the likely cause?

As a next step, I was thinking to check the fuse in the FEM as you suggested -- what is throwing me off however, is when I called the BMW dealership, they said there is no dedicated fuse that powers CA

Also, while before I wouldn't get any specific errors in the iDrive system, now I do get a Comfort Access Limited error every time I start the car, see attached.

Using a bigger wire is no problem. I would suspect the joint / soldering is more likely the cause of failure than a wrong gauge wire. If you are unsure, you can always go up in size.

If you have a multimeter, please measure the resistance of the driver antenna at the PINs on the fem side. I have written the PIN numbers in previous post. The resistance should be in a place between 0.2 - 5 ohm. This way you double check if your repair work is correct.

If you read what I said, that fuse is only for the sensor in the doorhandles. So BMW dealer is correct, there is no central fuse for CA. CA is a much bigger system than only the doorhandles.


Well that limited access is a step forward from complete failure, but message is useless. Need real error codes, this could still mean that one of the antennas is not connected. I had the same message when I unplugged one antenna.

Attached wire diagram for antennas

[anchovyslayer]

Hi, thanks for following up. I am not sure I fully understand your earlier picture pointing to pin 9 and 27 -- not sure how that translates to the FEM module components and how I can locate the pins you recommended.

[mrpingu]

Look at this video from the 2 minute mark to around 6 minutes.

This gives crash course in the pin system. The use the the images I posted earlier to locate the exact pins. Good luck