hi i have had problems on the early v/s40 with corrosion in the harness where it passes under the rad may be worth a visual/wriggle test there couldn't agree more with mark about the earth side of the circuit.
there is also a problem from memory about a multi plug within the engine bay fuse box.
i did a focus a few months ago with a very similar problem and when the multi plug in the fuse box was moved it was logging similar codes
i know its a bit vage but i cant remember the exact codes but it was a supply problem.
might be worth putting a scope or multi meter on the supply while routing in and under fuse box.
hth martin