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      06-01-2017, 12:47 AM   #1

Drives: 2008 328XI
Join Date: Jan 2017
Location: SoCal

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Question BMW Professional Hi-Fi Stereo - SOS Error and No Bluetooth/Aux (TCU Options?)

Hi all - longtime lurker on these boards and I have compiled a lot of information from the various posters here over the years. I really appreciate all of the helpful people on this board. I've searched within many threads and have found bits and pieces of info regarding the TCU but am wondering if anyone can simplify how to fix this problem as there is some conflicting information and I am not very knowledgeable about the electronics/coding.

Car: 2008 BMW 328XI (Production date 10/2007) that came with BMW Professional Radio and HiFi stereo, BMW Assist, Bluetooth, USB Audio, and provision for the 6CD changer but it was never installed.

Issue: Randomly went to start the car one day and I got the SOS/Phone Error within 10 seconds of starting the car. Yellow light with a slash through it, now it comes on every time I start the car. My option for Aux and Bluetooth Phone is now no longer illuminated in the Audio Menu and I can not get to any settings via the BMW Professional headunit for these inputs. The AM/FM/SAT radios all work as does the CD, but no AUX.

Issue2: I get a mild crackle pop through my speakers that is definitely annoying (in the working Audio modes of CD/AM/FM/SAT). The sound persists even when the radio is off which is when its most annoying.

Attempted Resolutions:

1) I first tried to reset the audio unit by holding the power and eject buttons down for 30 seconds but nothing happened so don't think I did anything.

2) I disconnected the battery and waited 10 minutes or so and then reconnected - issue still present.

3) I took it to a BMW dealer for a software upgrade / troubleshooting - not positive what version I had previously or whats on there now, but the noticeable difference is that I now have the radio station labels for the stations in my area (RDS I believe its called) and these never showed up before - only the numbers for the stations. I specifically asked if there was anyway to disable the SOS module and they told me no problem, we will get this fixed for you, then they had the car for 2 days and the SA was stumped and told me there was no way to 'bypass' the SOS function to return the Bluetooth functionality. I do not care about the SOS feature at all and would happily remove it to restore Bluetooth/AUX functionality and fix the radio pop. They told me they tried to reset and checked the fuses but everything was ok. They asked for an hour of labor to diagnose the problem (even though they had my car for 2 days already) but the SA suggested it was most likely the TCU and that it probably had a short in it. He didn't know much about the TCU or how it could obtain a short just that it could be the culprit. He seemed like a good guy and even offered to help me code a new TCU if I got the part installed myself.

Based on all of the above, I'd like to know what my options are to eliminate the crackle pop in the stereo and return Bluetooth/Aux functionality. I could even make do without Bluetooth as long as I can get the crackle pop to stop coming thru the speakers.


1) Does this sound like a "short" in the TCU or something else?

2) Can I replace the TCU with a model from a similar vintage BMW? Does it need to come from a system that has any similar components to ensure it works properly with my system? Will coding be required if i replace with a similar module? I saw some DIYs and this looks easy enough.

3) Would a MOST bypass work for my system where I just disconnect the TCU and hookup a bypass for this TCU component? Will I lose functionality to anything?

4)Can I code the SOS function out of the car and eliminate the error message? I don't think I would be comfortable doing this myself, but would be willing to hire a coder either locally or online who can perform the functions to restore Bluetooth/Aux while eliminating the SOS error? Any way to tell before doing the coding whether this would require replacement of the TCU as well?

5) Is there an upgrade or aftermarket solution that effectively will restore Bluetooth/Aux functionality that I am currently missing and make the pop crackle go away in the stereo?

Thanks in advance for your help, I know my way around under the hood mechanically, but these electrical and coding systems are way above my pay grade. If there is already a thread I haven't seen that explains all of this, please point the way but I haven't found anything after hours of research.

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      06-01-2017, 02:13 AM   #2
Major General

Drives: 325xi 06 wagon MT
Join Date: Jan 2010
Location: Santa Cruz, Ca

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If you have checked that there is no water in the amp area
the static could be your head unit going bad.
The other problem is likely the TCU .
I would replace it with a Mulf 2 hi that will get you USB .
That is if you want to remain OEM.
Programming will be required for either and the dealer may say
this is not possible or have a hard time doing it.
You should be able to find a coder in your area to help you with
the programming.



You can try a Most jumper to bypass the tcu
it won't make the SOS error on the display go away. You might want to see if it makes the static go away.
Aux and bluetooth come from the tCU.

Last edited by ctuna; 06-01-2017 at 02:21 AM.
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      06-14-2017, 06:50 PM   #3

Drives: 2009 335I X-Drive E90
Join Date: Nov 2012
Location: Orlando

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I recently had an SOS malfunction in my X5 and it turned out that my Satellite radio box stopped working. I had to use a MOST bypass to figure this out by connecting the fiber optic loop to the male connector after unplugging my satellite radio module and my auxillary came back. Once i replced my satellite module the SOS error went away.

Get a MOST bypass and unplug a module one at a time and plug in the bypass to see if anything starts working again. BMW has all the modules on the same MOST set so if one fails it screwes up the whole line. They are all installed in a cirular fasion so if the loop breaks you run into these probelms. If you have a water leak, look for rust on the modules if you see rust you probably found your problem.

I'd also suggest using ISTA/D Rheingold to see if any modules in your loop are no longer responding at all, if so that'll show you the module to concentrate on. Or you can use INPA and pull the codes and look for no communcation with module, for example my code was (S0162 - No communication possible with Satellite Tuner (US))
2009 335i X-Drive | GC Turbos | VTTO silicone cold/hotside, | Fuel It PI with FPR and return line and BMS controller | Fuel It Stage 3 fuel pump | BMS dual cone instakes | BMS Catch Can | VRSF 7.5" Race Intercooler | Forge Diverter Valves | JB4 G5 ISO with Blutooth/JB4 Mobile App | n20 tmap sensor 3.5 bar | AR Catless DP's
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