It's only monitoring level so I'd unplug the cable, I presume the light will then go on. Short the pins with a paperclip & electrical tape to insulate it, the light should go out. Now drive for a week or so manually keeping an eye on the coolant every now and again and watch out for the flashing light. If it stops flashing it's the expansion tank level meter or contact. If it keeps flashing it's the loom.