I have a 2002 ford escort zx2 the troubleshooting code po125?

My check engine light came on and the test showed the pcm has determined that the amount of time it took for the coolant temperature sensor to reach an input value consistant with closed loop operation was too excessive. What do I do to fix this? Termostat and gasket were mentioned. also coolant temperature sensor. Should I replace the thermostat first then try the sensor? what would you recomend?