MOST bus fault 2008 s80
 

Hi all,
My Audio(radio/cd/AUX), bluetooth phone connection and rear parking sensors have all failed, initially intermittently but after a few hours they failed completely!
I still have Climate info and can access car menu through the ICM (screen in center console) but have no access to any radio/phone functions including balance/fade.

I took it to an independent, who was only able to tell me there was a fault in the MOST ring but not where in the ring.
I asked on here was there anyone with a Dice+Vida in N.Ireland with no luck, so I bought myself a MOST loop to test the modules myself.

So far I have light at, and bypassed the AUD (amp) and IAM (radio/cd) to no avail.
I have no light at the ICM.
As best as I can work out I still have to locate and bypass the AUX and BPM(phone) modules, but I am struggling to find a MOST ring diagram that confirms this and the location of the modules.
Any help/suggestions would be greatly appreciated.

youll get diagram on vida it work backward and not forward so when you get diagram work the way back

where is your amp under seat?

im very surprised your indy dealler didnt conect to vida it would have given you a code also it would have told you on the network which unit s down highlighted in orange

(double post)

Here's the MY2008 onwards S80 audio system and MOST bus.
Not all devices may be fitted.
Eg RDAR is the digital satellite radio receiver, only for the USA.

https://www.volvoforums.org.uk/pictu...ictureid=10902

The signals go from ICM > IAM > BPM > AUD etc.

Hint:
The figure above applies to vehicles built up to and incl. structure week 200745. Vehicles built from and incl. structure week 200746, Integrated Audio Module (IAM) is placed second last, between Remote Digital Audio Receiver (RDAR) and Accessory USB unit (AUU).

If you see a red light on the fiber cable at a device, it means the previous device is transmitting
If not, the previous device is not transmitting
Once you find a device not transmitting, work backwards until you find a transmitting device. Then you know where the light is stopping.

Note that you may have a device fault or a cable fault.

And if you are thinking of replacing units, note this:


The Infotainment Theft Protection (ITP) function is designed to prevent non-approved control modules from being installed in the infotainment system. This is to prevent the theft of units.

The function is controlled by the infotainment control module (ICM). The infotainment control module (ICM) (3/281) checks the serial number on all control modules in the MOST network and the High Level Display Front (HLDF) (16/46) and compares these with a list stored in the central electronic module (CEM). The list is transmitted to the infotainment control module (ICM) via the controller area network (CAN). The infotainment control module (ICM) retrieves data about the serial number of the control modules via the MOST network. The infotainment control module (ICM) compares the information with the stored serial numbers.

If a control module is not in the stored list, it is disconnected from the MOST network and the functionality of this control module is blocked. This means that control modules in the MOST network cannot be moved from one vehicle to another. This function also applies to the High Level Display Front (HLDF), which communicates with the infotainment control module (ICM) via the controller area network (CAN).
If a control module is not included in the stored list or if a control module in the stored list responds incorrectly, then a diagnostic trouble code (DTC) is stored in the infotainment control module (ICM).
For further information, see Design and Function, MOST.

And it is MUCH easier to diagnose using VIDA:

Ring break diagnostics

General
This function is important when fault-tracing the MOST network. Ring break diagnostics are used when there is an open-circuit in the MOST network and diagnostic trouble code (DTC) ICM-U1A2400 has been stored in the infotainment control module (ICM).
During ring break diagnostics, all control modules transmit a message to the infotainment control module (ICM) in reverse order to their position on the MOST network. This means that the Accessory USB unit (AUU) transmits first, not last.
The control module which is not working will not transmit a response to the infotainment control module (ICM). This also means that the control modules which are connected before the defective control module will be unable to transmit a message to the infotainment control module (ICM).
The same applies to open-circuits in the optical cable in the MOST network. No control module before the open-circuit will transmit a message to the infotainment control module (ICM). By using the incoming messages the infotainment control module (ICM) can present at which control module the open-circuit has occurred.

SwissXC90,
Thank you very much for the diagram and info, it is what I was looking for! From the diagram i recon it has to be the AUU (not sure if the SWM will affect the MOST ring) which i think is located under the arm rest area.
If a second hand component is fitted can VIDA reprogram it?

Don't guess.
Be certain before buying a replacement device.
Use VIDA!

Note that VIDA can only program virgin devices (for anti-theft reasons)

Thus a unit from another vehicle will be rejected by your vehicle, as it has the wrong serial number.

So if you have a failled device, your options are very limited:
1. Repair of the device by eg https://volvodiagnostic.com/shop/index.php
2. Fitting of a brand new device (and of course programming the car to accept it)

This happened to my S80 2007, dealer replaced the mail unit behind the dash and still the same, mine was the unit that controls the USB and iPhone connector. Forget the name of the module.


I did post about it so should show up on a search.

Edit, looking at the above it might have been the AUU.

Update,
Located the AUU today with great difficulty, stripped the center console out to discover it located under the carpet where the front seat passengers right foot would be (right hand drive car) if they straightened their legs out.

The AUU has a male MOST loop connector on it but it incorporates at 4pin plug with it, so the standard female MOST loop connector I was using to bypass each component wouldn't fit. I was able to take the fiber out of the female connector and manually hold the ends onto the MOST ring, where the AUU connects into the ring, long enough for the radio etc, to work again :)

When I opened the AUU I discovered evidence of water ingress through the connector and across the circuit board.
next steps are;
1; locate and seal where water is getting into foot-well.
2; clean board with alcohol based cleaner (no visual signs of scorching)
3; follow the options as suggested by SwissXC90 above.

I will update on the final outcome in case it will be helpful to others in the future.