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E90/E91/E92/E93 (2006 - 2013)
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  #1  
Old 02-05-2016, 01:26 AM
1gaz9000 1gaz9000 is online now
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Mein Auto: e91 330d
2008 pre-lci CCC MOST cable failure

Hi All,

In the process of taking out my Professional HU I've managed to crack the MOST cable. I think. HU was removed and the red light could be seen in the cable end when it was tucked back in, then a few days later it was not lit. idrive is goosed and SOS calls and TPM system is chucking errors. Could be a fuse or one of the modules and I'm in the process of trying to gather as much info as possible, but my gut tells me its the 7M long fragile cable that runs to the boot. That would be just my luck and a lesson to be more careful in future.

I've got a UK 2008, pre-LCI e91 330d AT with CCC. BMW want 33 for the part and additional 243 in labour to fit a new 61120142318 (http://www.realoem.com/bmw/enUS/show...diagId=61_1578)
I'll probably just let them do it assuming I can diagnose that its definately that. Dunno if I can be bothered to rip up all the trim and carpet and find I've still not resolved the issue!

However, I'm still trying to get to grips with the whole MOST concept, and its my understanding that theyre all linked and daisy chained from the one source but how many fibre optic cables are there running front to back? I see that the system loops and you have two transmission directions. So, are all the modules contained at the rear of the car, with the exception of the CCC? One of the docs says that this "Counts as 2". What exactly does this mean? Will I likely need to replace further cables here?!

This is my current reading list. Does anyone know where I can get a better understanding?

http://www.bmwlogicseven.com/wp-cont.../07/image1.jpg

http://www.bmwmotorsports.org/BMW_docs/mostbus.pdf

http://www.bimmerfest.com/forums/sho...d.php?t=842131

Thanks for any help you can give me.
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  #2  
Old 02-07-2016, 02:22 PM
anees anees is offline
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Location: Woking, England
 
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Mein Auto: BMW E46 316i
There are only two cables per MOST unit ie. transmit and receive.

There is a MOST connect bridge under the left back seat shoulder bolster. This is where your L7 amp, cd shuttle, telematics would connect to, instead of having a long continuous fibre optic cable running from the back to the front of the car.

From your description, the break in the fibre optic is from your head unit to this bridge.

BMW will have to remove head unit, install the new fibre along the nearside cable guides.

Have a read at the attached document.
Attached Files
File Type: pdf 08_E90 Entertain and Communication.pdf (1.98 MB, 8 views)
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  #3  
Old Yesterday, 02:10 AM
1gaz9000 1gaz9000 is online now
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Mein Auto: e91 330d
Thanks for your comments - they're very much appreciated.

I've had a read of the circuit diagram and its useful. Particularly this part:

And I've managed to find actual photos of the parts mentioned in it...
http://www.bmwfanatics.co.za/showthread.php?tid=47900

Armed with a little bit more knowledge, I could potentially just purchase one cable (the transmit, as theres no red light showing in existing one?) plug it into the bridge, and then see if it lights up? Then CAREFULLY and loosely run it up the middle of the car to the HU and connect in the rear to see that the CCC is now responsive and the screen comes back to life. Got to be worth a punt for thirty quid? I guess I could still have an issue if I've managed to wreck the 'receive' cable as well? I wish the diagram showed TWO cables running this loop!

I guess what I still dont know the answer to is, if this cable is replaced, would the loss of the screen, SOS/TPM warnings likely be resolved? I know they're all connected, but can no other systems, or the CIC, function independently of the CCC? I read one post that said the CIC can still work

I'm keen to do as much of the fault finding before BMW quote me a new CCC + labour + coding when it might be something very straightforward!

Thanks again
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  #4  
Old Yesterday, 01:28 PM
anees anees is offline
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Location: Woking, England
 
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Mein Auto: BMW E46 316i
This is a good start, to loosely run a fibre to the MOST bridge.

The way the MOST devices work is all in a loop. If the loop is broken, then you will get problems. Also, if one of the devices are faulty, this will drag down the entire loop.

If you were experiencing error messages prior to the fibre break, it would suggest that one of the devices in your MOST chain is faulty.

Some useless piece of info: in the new F models of the 3 series, BMW are switching to a mix of copper and fibre. As the space in a car is small and confined, they can run copper cables and get very high bit rates with low or no interference.


Quote:
Originally Posted by 1gaz9000 View Post

Armed with a little bit more knowledge, I could potentially just purchase one cable (the transmit, as theres no red light showing in existing one?) plug it into the bridge, and then see if it lights up? Then CAREFULLY and loosely run it up the middle of the car to the HU and connect in the rear to see that the CCC is now responsive and the screen comes back to life. Got to be worth a punt for thirty quid? I guess I could still have an issue if I've managed to wreck the 'receive' cable as well? I wish the diagram showed TWO cables running this loop!

I guess what I still dont know the answer to is, if this cable is replaced, would the loss of the screen, SOS/TPM warnings likely be resolved? I know they're all connected, but can no other systems, or the CIC, function independently of the CCC? I read one post that said the CIC can still work

I'm keen to do as much of the fault finding before BMW quote me a new CCC + labour + coding when it might be something very straightforward!

Thanks again
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  #5  
Old Yesterday, 02:06 PM
fdriller9 fdriller9 is online now
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Mein Auto: '06 AW 330xi
A failing module can also cause your symptoms.

I would first try and remove accessories from the MOST bus to eliminate other modules as culprits.

You can purchase a loop back connector to remove the modules temporarily.
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