I have 1989 jaguar xj6 the instrument cluster and radio went out at the same time could it be ecm or fuse went bad?

it is most likely the fuse. I have a 1984 jaguar xj6 and i have had the same problem, my fix for it was that the fuse box was messed up and a lot of the fuses have to be half out to work. Just try testing the fuses and moving them around a bit to see if that will re-connect the instruments.