Update. I’ve gone though the optical cables and can’t find a fault. I’m getting light at the diagnostic connection at the glovebox which implies the TCU is connected ok as its upstream of it. When I shine a light on the diag plug I also get a light at the mask most connector.( should I see it at both fibres? I.e back through the TCU to the mask ?)

When I try to communicate with the TCU I get coapi2020 IFH-0009 error(no response)

I’m a bit stumped now.