Hopefully this post helps someone if they experience a similar problem as I did over the last 11 months. My problems started last summer and have continued intermittently since then. My problem was first reported within the following post:

https://www.fullfatrr.com/forum/topic48133.html

To summarize the problem and symptoms that I experienced (vehicle 2010 RR 5.0L HSE, north american version)

Driving along the music would suddenly stop playing, followed by Tyre Pressure Monitoring system not available, Blind Spot Monitoring not available, then the radio screen would go blank and orange light flashing in the radio power knob. In addition the HVAC system would shut down. Typically things would eventually reboot and system would be fine. If these faults popped up while parked or locked. You could not start the vehicle or even get into it if the vehicle was locked. The smart key not found warning would be displayed on the TFT screen.

I spent endless hours searching the internet, this forum, Topix, reviewing wiring diagrams and schematics, etc. etc.

I have both a Nanocom and a GAP IID BT tool that helped in the diagnosis. I thought the Nanocom was great but in my opinion the IID BT tool is exceptional and Patrick M. at GAP Diagnostics was incredibly helpful....I highly recommend the tool and their customer engagement.

The diagnosis indicated a whole host of Medium Speed CAN faults. There was so many of them that it was difficult to sort through them. Something that eventually became clear was that the entire Medium Speed CAN bus network would crash and most or all of those systems would be inoperable. Most ECU's on the MS CAN Bus are peripheral systems that aren't truly needed to get from point A to point B except the Keyless Vehicle Module (KVM) which would prevent the vehicle from starting. Thus if the MS CAN network goes down you are about to be stranded if you shut the vehicle off!

I went through the common problem areas including
1. Weak battery (replaced twice to no avail)
2. Bad alternator (poor charging, scoped for AC ripple within charging system, etc.). Replaced alternator because it was nine years old even though all tests indicated that it was fine. Again, this did not solve my problem.
3. Searched everywhere for water ingress as I have read this has been common in earlier models....I never found any evidence of water ingress or corrosion of contacts.

In discussions with GAP Diagnostics, Patrick indicated that he believe it was likely a wiring problem vs an ECU problem. Specifically either a short to ground or a short to 12V on either the MS CAN Bus high or low lines. The MS CAN bus wiring is two twisted wires that connect all of the ECUs on the network together so that they can send information between each other.

Anyway to make a long story short, I happen to find in the driver side (North American vehicle) rear cubby that the MS CAN Bus wiring passed between the pressed metal bracket holding the parking aid ECU and the exterior insulation. The space was not much larger than the MS CAN wires and the edge of the metal bracket was very sharp. I believe over time vibration has caused the wiring to agitate against the sharp metal edge and thus short the MS CAN network to ground causing the entire network to crash. Jiggling the wires would cause the problem to come and go. To address the problem I placed a section of corrugated plastic sheathing over the wiring to prevent grounding. I have attached a picture to show the location (red arrow) where the problem was located and where I installed the sheathing. The yellow arrow shows a very small section of the green MS CAN bus wires poking out from the sheathing. I am back to enjoying this great machine which has been very reliable except for this.

Click image to enlarge

A great job to find the cause and thanks for the warning of where it was.

A similar canbus problem on a D4 was found by unplugging each connector or module along the bus until the fault stopped occurring but if in the main front to rear harness then the short could be very hard to find.

Thanks Graeme, yes I originally thought the problem was one of the ECU's or the Central Junction Box. I was not looking forward to digging into the CJB. The folks at GAP thought it was more likely a wiring problem and specifically a short to ground or short to 12V. I spent a lot of time reading about the CAN Bus system how it works, locations of ECUs etc. If a single ECU goes down it doesn't typically cause the entire network to go down. Similiarly corroded connections would lead to Non-communicating fault codes passed that point in the network, everything upstream would typically still function normally. For these reasons and likely a few others GAP pointed to short circuits in the network. The short circuits would prevent all ECUs from transmitting any useful data between each other. As a result the Fault Codes read by both my NanoCom and the IID BT tool were Non-communication faults between every ECU on the MS CAN network.

I found the problem by accident actually. I wasn't really sure where to start and since a lot of MS CAN network components are in the rear of the truck. I decided to look there. The parking aid module is one of the easiest to get to and while I was examining it I bumped the large loom beside it, the truck was running at the time and instantly the MS CAN network woke up. Upon further investigation it was not the large loom but the two twisted MS CAN wires next to the loom that would crash or wake up the network when manipulated.

My overall description and timeline presented here are pretty simple and straight forward but honestly this problem was literally a needle in the haystack issue.

Taking this to a dealer or potentially even an Indy repair shop could cost thousands to track it down. The dealer Land Rover Ottawa was very good about it but I can only imagine there perspective...we are going to spend 10's to 100's of hours searching for a problem with no guarantee that we will find a problem. The customer could end up with a massive bill and still have a broken truck...not a great recipe for anyone.

Overall, I learned lot, got my truck back to being dependable, the repair was low cost, I did end up replacing battery and alternator but those where OK preventative maintenance items anyway.

Again hopefully this helps some one else out if they find themselves in similar situation.

Update

My expeience with Land Rover electrical repairs has been that you need a little time to know for sure it has been fixed! I am happy to report that since adding the small piece of shielding to the MED Speed CAN Bus wire mentioned above I have had absolutely no reoccurrence. This is now 4 to 5 months of use.

Thank you for the write up. I just lost my radio today and used the GAP IID Tool and got the codes for "Control Module Output Power A - General Electrical failure - circuit short to ground or open"

Was this similar to your fault? Should I start in the back of the car as well?

2010 5.0 HSE Nara Bronze

Sounds a little different. Mine had faults for most if not all modules on the Med Speed CAN bus. If you just have the one listed for the radio it maybe more localized.