Radio keeps cutting out on my car. 2007 model year XJ VDP built December 2006. Apparently I need an 'optical loop' to diagnose which component of the fibre optic system needs to be repaired. Does anyone happen to know which exact part I need? There are many such 'optical loops' available on the internet but I can't be sure which is the exact one. Any help appreciated.

 

The Black Optic Fibre 'link lead' selection is listed in a TSB we got at the dealer decades ago.
Parts might be NLA by now.
A shop with a selection of fibre optics and connectors should be able to concoct a set of 'link leads'.

 

I think you need a Jaguar D2B optic bypass loop to troubleshoot the D2B optic ring. These are common and very useful because you can bypass each different component separately in the D2B ring to quickly isolate which one is bad. Note the components MUST be connected in the order shown in the attached document. So don't get them confused. The good thing is Jaguar does label these different cables pretty well.

Sorry I don't have the JLR part number for the bypass/jumper.
I circled it in red below.





Be sure and note the part number matrix in Karl's document. In case you do want to make changes it requires a unique cable.

It seems the MB/BMW also use the same type of optic ring. But do check your car matches the plugs shown in this ad.
Here is a pair of loops for $15.
Fiber Optic Bypass Loop

Here is a great link about a home made bypass and the optic network.
DIY Optic Bypass
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Who is Karl????????????
motorcarman = bob gauff in TX. (ME)

 

Oops! I am very sorry!
Got confused in my old age I guess.
I will rephrase that " Be sure and note the part number matrix in Motorcarman's document"
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I don't know but wow your car is gorgeous. Indigo Blue?