1985 Xjsc V12 Aftermarket immobiliser.

[Td5_Discovery]

So we’ve got a 1985 V12 XjSc that I’m trying to get running for my customer. It’s been off the road since 2018 and appears to have a aftermarket auto watch immobiliser that I’m guessing has died while it’s been sat. Any ideas where it could be located to bypass it?

Tried looking in the obvious places: In both passenger and driver knee/footwells, glovebox etc.

Thanks