[papandrea]

Hi there, I have a 2007 E90 323i. On my CCC head unit I have the option to select aux input for audio (it is not greyed out, it is bright white). My issue is when I select aux it shows the aux screen for a split second then returns it to the FM radio selection. Even if I select AM radio and then select AUX it randomly returns to FM radio. I have tried selecting AUX with my phone plugged into the AUX input jack with no difference. I have inspected my MULF unit also for any obvious damage with no luck. I have tried disconnecting/reconnecting the battery with no luck. I have checked that the AUX input jack is correctly plugged into its wires with no luck. Lastly, I have checked that the fibre optic cables between the MULF and the CCC head unit are both properly connected and both have red light emitting from ether end.

[ptpending]

you need to tell which type of the mulf you have
take the picture from its label

[papandrea]

Originally Posted by ptpending

you need to tell which type of the mulf you have
take the picture from its label

Hi there, its named a MULF 2 high SVS. I don't know what that means specifically, and I don't have a very good understanding of what exactly these modules do. See attached photos as well for exact details. Kind regards

[ptpending]

ok, thanks
that means that your aux is routed to MULF2HIGH, and not directly to headunit
you need to perform that MOST bus test to understand if MULF2high is operational and MOST bus is closed

if MULF2HIGH will not emit any red light in most connector, then you have either its fuse burnt, or module failed and should be replaced and coded

[papandrea]

Hi there, I have done the MOST bus test, I discovered that the MULF 2 HIGH module wasn't emitting any red light despite having red light being input into it. I did this by checking for red light downstream of the module at the diagnostic connector under the glove box.

Using a bypass connector I was able to complete the circuit of red light all around the MOST bus. However this did not fix my issue of being unable to connect to the aux input setting. The reason I tried this is because on my 2005 BMW E90 I can successfully select aux input when the MULF unit is disconnected (however there is the difference of the aux input not having the USB port next to it, whereas on this E90 there is a USB port next to my aux port).

So in conclusion, i believe that either my MULF 2 HIGH module or radio unit is faulty. Unsure of which one to replace first.

[ptpending]

mulf2high is dead or its fuse is dead
so you can check the red and brown wires in blue plug
if they have 12v then MULF2high died
if you have not 12v, then fuse is fried and should be replaced at least

[papandrea]

Hi there, sorry haven't had much time to work on the AUX issue but I value the help! I've used my multimeter to test for 12V on the blue connector that connects to the MULF module. Testing the red and brown wires I do not get 12V, it's showing basically nothing on about 0.1 volts. So I thought I'd have at all the fuses related to the radio and cd system as indicated by my fuse card, but couldn't find any faulty fuses. I checked the fuses for continuity with multimeter. Are there any other things to investigate that could cause no 12V power to be reaching my MULF? Kind regards!

[ptpending]

check the Fuse 26 if car is made until 2007/09 month and Fuse 13 if car is made after 2007/09

[papandrea]

Fuse and 12V supply has been fixed up now, thanks for you help! I'm still having no fibre optic (red light output) coming out of my MULF module, even though it is being powered up and I have confirmed there is no other break in the MOST loop by using a bypass connector to skip the MULF module. So in conclusion I'm fairly certain I have isolated the problem to the MULF module itself and I'm currently looking for a replacement. I'll make a post if replacing the MULF module fixes this fault for future reference if anyone else ever has the same issue. Thankyou ptpending

[ctuna]

If you have the 6fl option = usb I believe the aux may come from the Mulf 2 hi .
http://www.e90post.com/forums/showthread.php?t=1181654

There where no mulfs in 2005

[ptpending]

Originally Posted by papandrea

Fuse and 12V supply has been fixed up now, thanks for you help! I'm still having no fibre optic (red light output) coming out of my MULF module, even though it is being powered up and I have confirmed there is no other break in the MOST loop by using a bypass connector to skip the MULF module. So in conclusion I'm fairly certain I have isolated the problem to the MULF module itself and I'm currently looking for a replacement. I'll make a post if replacing the MULF module fixes this fault for future reference if anyone else ever has the same issue. Thankyou ptpending

so the module died and burnt the fuse
you can repair the module by yourself or by local repairer who can trace 12v supply circuit on MULF board,
i had such a case 14 years ago with my first MULF2HIGH