Ring Loop MOST issue

[EdmundIJones]

I have decided it's time to sell my 2004 XC90 so took it to my local hand wash for a full valet, they did a first class job and it's never looked as new. BUT, while washing the carpets they have obviously caused some sort of problem as this morning the radio want turn on and the sat nav won't raise.

There is power getting to the radio as I got it to bring up the welcome message and then it went blank again. I can use VIDA to activate the buttons and see the state of the buttons when I press them so there is some sort of power/connectivity.

There is an ICM communicators error that comes up and reading the details it says there could be a ring loop / MOST issue. I'm not so good at this point of technical detail but it seems to me like maybe moisture or condensation has got into the fiber optic MOST cable which could be causing a communications error OR maybe one of the ring modules has been knocked.

Can anyone explain how to use VIDA to try and track down the route of the issue, it talks about pulling the ATM fuse for 30 minutes but I can't even find reference of which fuse it is.

Help!

[SwissXC90]

Remove the audio amplifier under the right front seat.

The MOST bus goes via the audio amplifier

Check the amp for water ingress.

The fiber is the orange cable, ensure it is not damaged.
Make sure the amp has power (measure it)
If anything is wet, remove it and dry it thoroughly

Note that the gyro sensor is also in the same hole, I believe

[EdmundIJones]

Thank you SwissXC90, appart from the amp are there any other ICM related modules aroudn the floor areas where they could get wet from carpet washing?

I've read you can use an optical loop lead to bypass the amp etc if it is damaged.

[KBB]

Just add MOST fibre cables do not like sharp radius bends in them as it disrupts the light beam. Check the routing of the cables that were likely in the vicinity of a valeter. They may have moved accidently a fibre cable and bent it beyond its working radius.

[EdmundIJones]

Thanks for this also. It's dark now so I'll have a prod around after work. Maybe take the drives seat out to give full access.

[SwissXC90]

Originally Posted by EdmundIJones

Thanks for this also. It's dark now so I'll have a prod around after work. Maybe take the drives seat out to give full access.

Dark is perfect
On every fibre cable you should see one emitting red light (the optics are generally in the visible red spectrum)

Refer to the wiring diagram of your car:
http://www.volvowiringdiagrams.com/

If you cannot find your model year, choose the closest model, the MOST bus is the same in all the models

[Dashing]

I have a Volvo xc60 2016. My infotainment system freezes and restarts every two to three minutes. I checked the MOST fibre cable leading into the amp. The cable gives a red light but there is no red light coming from the amp.

Dice is giving this error. ICM-U1A1587 Incomplete MOST Ring Reported By IHU - Bus
Signal / Message Failures - Missing message

Your help is extremely appreciated!

[SwissXC90]

Originally Posted by Dashing

I have a Volvo xc60 2016. My infotainment system freezes and restarts every two to three minutes. I checked the MOST fibre cable leading into the amp. The cable gives a red light but there is no red light coming from the amp.

Dice is giving this error. ICM-U1A1587 Incomplete MOST Ring Reported By IHU - Bus
Signal / Message Failures - Missing message

Your help is extremely appreciated!

Sounds like you identified where the issue is. Anyway, VIDA gives a very good most ring bus diagnostic description to find the faulty device or broken cable, just follow what is written in vida.

[Dashing]

Thank you for your swift response I really appreciate it. I don’t have Vida or DICE. I took it to a Volvo dealership and they gave me the code. They want me to book in the car for a further 2 days to “diagnose” it. I must pay them a fee to diagnose it and only afterwards they will “quote” me to fix it. So basically an arm and a leg.

I’m thinking of taking out the amp out to inspect. Hoping it is really something simple.

[SwissXC90]

Originally Posted by Dashing

Thank you for your swift response I really appreciate it. I don’t have Vida or DICE. I took it to a Volvo dealership and they gave me the code. They want me to book in the car for a further 2 days to “diagnose” it. I must pay them a fee to diagnose it and only afterwards they will “quote” me to fix it. So basically an arm and a leg.

I’m thinking of taking out the amp out to inspect. Hoping it is really something simple.

if you have no diagnostic tools you are stuck.

VIDA tells you how to do a ring break diagnosis. You can also temporarily bridge the fiber optic line of a suspect bad device to determine if the ring comes back up.

I suggest asking on this forum for anyone with VIDA who is located close to you. I'd happily help if you come to my house, I live in the original CrossCountry, in the alps in the middle of Europe