Engine Coolant Sensor and Gauge

My 98 Catera has gone through the well known issues with the Oil Cooler leaking in to the coolant. So I have replaced the Oil Cooler, Water Crossover, Radiator, All Rubber Hoses, Thermostat, Engine Coolant Sensor for the Gauge, and the washers for the Bolts that hold down the Crossover and the Oil Cooler. The problem I'm having is that my Temp Gauge on the dashboard is always showing completely cold, the needle is slammed down.... I've done a resistance check on the sensor and it shows an ohms reading that isnt within specs for the temp that it was at. I also did a continuity and resistance check on the wires between the sensor and it splice point and between the splice point and the dash with correct readings. Any suggestions?????

get a scan tool and do a gauge sweep test to see if the gauge inself
working.