I have a 2009 X250 where the infotainment screen fails to complete the boot up. It’s obviously trying but the Jaguar flash screen keeps cycling.
I have scanned the car and it returns two fault codes U1 A1 5-87 (Incomplete MOST ring reported by infotainment control module) & U1 A24 -00 (MOST ring complete no communication).
There are a lot of modules on the ring and I started looking at the easiest place to access the modules which is left hand side of the boot. The main amplifier, DAB receiver, navigation computer and TV tuner are all in a block. There appears to be only one fibre connection from there into the main harness going towards the front of the car. I have unplugged it and I see no light. According to the service manual, this should go directly from the amplifier to the Infotainment Control Module. The ICM is a bear to get at because you have to pull the dash apart as it sits under the Integrated Audio Module (dash mounted CD player etc).
I have lots of questions about this but the first one is does anyone know the routing of the fibre in the harness? I suspect there may be junction under the left hand front seat. If anyone has knowledge of the MOST ring I would appreciate if it could be shared.
I can now post the answer to my own question in case it helps anyone else. On the MOST network, the TX of a module is connected to the RX of the next module in the chain. Exactly how it’s connected depends on the spec. of the car and how many modules you have.
The ICM provides the master clock and this is the order in which the following units are connected: ICM TX to MOST diagnostic/upgrade socket (not OBD socket) then to the RX of the touch screen. This terminates in a connector underneath the central console.
If there are no options in the boot, two jumpers join the TX of the Touch Screen to the RX of the IAM and the TX of the IAM back to the RX of the ICM thereby completing the ring.
If other options are fitted, the TX of the Touch Screen is connected to the RX of the Bluetooth module and is looped through the Portable Audio Interface if fitted. Both these modules are under the LH front seat. The TX of this combination goes back the RX of the IAM. If there are modules in the boot, a long pair of fibres (just over 4m) in the main harness take the TX from the IAM to whatever modules are fitted (Navigation, main audio amplifier, DAB/SARS receiver & TV tuner) with the last TX of these modules going back to the going back to the RX of the ICM thereby completing the ring.
The modules in the boot are on the left hand side behind the trim. There is a convenient connector in the boot where you can look to see if you have any light. I didn’t find any.
I then had to remove the LH front seat, which can be tilted back enough and with a bit of bodgery so you don’t have to take it out of the car. You can lift the leading edge of the B post trim enough to pull the carpet out of the way.
When I checked at the end of the link cable, I had light and so I looped out the Bluetooth module and the system came back to life. While the optical connector was OK, the power connector on the BT module I found to be very corroded and I’m not sure that I can save it.
This remains a work in progress.
Just to tidy this up in case anyone out there is interested, I bought a used Bluetooth module with a slightly later code which did not require any programming and this fixed the problem.
Thanks for all the info, will maybe come in handy in the future.