The coolant temperature indicator system includes a gauge and a sensor, the gauge is mounted in the instrument panel and the sensor is mounted on the engine block. Test the circuit by grounding the wire to the sensor with the ignition on and if the gauge responds, it's fine; if not, check the wiring circuit. To replace the sensor, unscrew it from the engine and quickly replace it with a new one using a sealant and check the coolant level after installing the new sensor.