Do you get any warning lights when you turn the key on?
Checking the Enthusiast’s Shop Manual, here are a couple things to try:
Water temp gauge = Check the blue-black wire which runs between the sensor and the 2L terminal at the instrument panel. A reading of continuity indicates the wire is intact, infinite resistance indicates a break in the wire, and continuity to between wire & ground indicates a short.
Does sound like a ground.....