[ayyy]

Hey all,

Don't ask me how, but three small wires in a large bundle behind the driver's side trunk lining that lead to the TCU got cut/damaged, resulting in a multitude of errors. These three wires are blue/white, yellow/white, and black/red. Very high gauge (thin) wires. I quickly got the soldering gun and re-connected the wires, but IN ADDITION TO THESE THREE WIRES, one thick black wire was damaged to the point of visible wire inside the black shielding, but not cut through. This I've read might be a MOST fiber optic line. I am currently getting the following errors:

- SOS Call System Malfunction
- No audio whatsoever (alert tones, radio, etc.)
- AUX cable not recognized (iPod is plugged in via aux cable but the option to switch to AUX is greyed out)

There is a very similar thread found here that outlines the same issue, but obviously I know the cause of mine which is different from the OP. I have tried the "3 finger salute" to reset the iDrive by holding down both eject buttons and volume button until it turns off and reboots. Still the same issues. The reply below on that thread might shed some light, but since I reconnected all the disconnected wires, therefore relinking the system, should it not be solved?

You have a fault in the cars MOST system. The MOST system is a fiber optic network that connects all of the components you described. It works on a loop topology so if one component fails or there is a break in the fiber, none of the other components will function.

Perhaps it's as simple as resetting my battery or giving it a while to reset on its own? Just want to get some opinions before I take it to the dealer.

Thanks in advance!


EDIT: found this on bimmerfest where someone else's MOST lines were cut:

He basically cut through all the MOST bus lines. There are only a few speaker wires cut. I would just solder the speaker wires and run new MOST bus lines. Will take 5-6 hours tops.

I'm now thinking maybe the MOST line that was damaged with exposed wire is the culprit? Can just that one MOST line be repaired if that's the case without an entirely new wiring harness being needed? Perhaps health fiber optic wire can be sliced in where the damage is?

[ctuna]

If you have a 2009 or older you have pre wiring
at least in the US.
Chances are there is a spare most cable for the satalite
or compact disk changer that you could substitute.
How the hell did this get cut ?This t seems pretty impossible
as the TCU/Mulf is located in the center of the car.
A Most line will have fiberoptics in the center easy to tell.
Put up pictures.

[ayyy]

Originally Posted by ctuna

If you have a 2009 or older you have pre wiring
at least in the US.
Chances are there is a spare most cable for the satalite
or compact disk changer that you could substitute.
How the hell did this get cut ?This t seems pretty impossible
as the TCU/Mulf is located in the center of the car.
A Most line will have fiberoptics in the center easy to tell.
Put up pictures.

Thanks for the reply, will put up photos as soon as I can. Car is out of my hands until tomorrow evening.

To confess, and this is to be a lesson for anyone as dumb as me, I was drilling a hole in my trunk liner to access the top mounts for my rear shocks. It was after a 12 hour air ride suspension install and I wanted a quick way to adjust the damping of my rear shocks without having to remove the trunk liner every time. So I was holding the lining out with one hand and eyeballing where to drill a pilot hole, but when it popped through it caught that wire bundle. So the wires are cut real high up on the driver's side near the shock top mount. Again photos coming tomorrow evening.

My car is a 2008 E92 335xi (sorry for not specifying earlier). It has an aftermarket IB subwoofer and amp; sub wires are T-tapped coming from the L7 amp. Is this something the local dealer will know how to fix (if there is damage to the MOST fiber optic cable and they can splice in a spare or use one that you mentioned? Or should I only trust an expert for this? I am obviously out of warranty.

[ctuna]

You need special tools to splice the ends of a fiberoptic cable
I don't know about splicing the middle . Better to just get a new cable
and replace it. There used to be a compact disk changer fiberoptic running
to the trunk and if it is unused I would use that as the new fiberoptic
to the amp. You need to backtrack the one you broke to the fiberoptic hub
behind the rear seat drivers side bolster and put a new fiberoptic cable in
or route the one from the compact disk changer option.

The dealer should be able to fix it but its likely they will empty your wallet.

[ayyy]

Actually won't have my car to take photos of the trouble spot until Saturday now.

Do you have a rough idea of how much a dealer would cost to replace that line? Given that they look at the wire bundle and determine that's where the problem lies? Are there specialized BMW MOST technicians that I would be able to find in my area? I'm just scared I'm gonna mess something up even more than it is now if I start yanking out fiber optic lines and trying to replace them given that I know nothing about this stuff. How easy would it be to replace the damaged line if I can even determine that there is an unused one I can borrow?

Thanks again by the way for helping me out.

[ctuna]

Fiberoptic lines can't short just take a look at it .
It should be real straight forward. It the electrical connections
I would worry about.
No such thing as Most technician.
I have no way of telling what it will cost usually labor from BMW
is over 120 and hour.

[ayyy]

hey all,

some photos here of the soldered wires that were completely disconnected:


Soldering job is janky but the wires are definitely all connected.

And a closeup of the (what I think is) the fiber optic cable that was damaged. Is this actually a fiber optic cable? As the exposed wiring inside just looks like copper like any other electrical wire:


You can faintly see a purple-shielded wire inside as well as another shielded wire. You can make out the text printed on the black outer shielding as "Gebauer & Griller 8 379...." but shielding was damaged so don't know the rest.

Thanks in advance for any other opinions!

Dan

[ctuna]

Fiber optic lines are the black corrugated and maybe the green lines.
NO wire in them so it should be very obvious which one they are.

[russ9898]

This is a completely uneducated guess but due to the size of the thick black cable i suspect it could be power or a ground connection? If so, might be worth checking your fuses as you could have blown one when it shorted out.

[ayyy]

Originally Posted by ctuna

Fiber optic lines are the black corrugated and maybe the green lines.
NO wire in them so it should be very obvious which one they are.

oh, so you're saying that black shielded one is definitely NOT a fiber optic wire? None of the corrugated/loomed wire nor any green ones were damaged.

So would that mean that maybe the soldered wires aren't perfectly connected? Or that the damaged black shielded one needs to be looked at further?

[ayyy]

Originally Posted by russ9898

This is a completely uneducated guess but due to the size of the thick black cable i suspect it could be power or a ground connection? If so, might be worth checking your fuses as you could have blown one when it shorted out.

Holy hell YOU ARE A GODSEND WHOEVER YOU ARE you just saved me probably $500 that the dealership would've charged me to replace that entire wire bundle. It was the 53 fuse that is a little 5-amp bad boy, the 3rd one listed next to the phone icon in the fuse diagram. The first two were fine but replaced them anyway, and when I got to the 3rd one it was completely fried. Started the car up and have NO errors and key chimes, stereo, aux-in works PERFECTLY.

Seriously you have no idea how happy I am. One less thing to worry about now.

Thanks again and to ctuna for the help these past couple days!

[russ9898]

Haha no problem, glad I could be of assistance and that your audio is alive again.