Drain the engine coolant, remove the air filter housing, and disconnect the electrical connector from the ECT sensor. Unscrew and remove the ECT sensor and remove and discard the old O-ring. Tighten the ECT sensor to the correct torque, refill the cooling system, raise the vehicle, and support it securely on jackstands. Remove the lower splash shield, unplug the electrical connector, and untighten the sensor from the radiator. To reinstall, switch the removal steps going from the final step to the beginning step. Install a new O-ring on the sensor, tighten the ECT sensor securely, and refill the cooling system.