In the case of a four-cylinder engine, the buyer should start with the draining of the cooling system. The ECT sensor is mounted on the water outlet housing at left side of cylinder head. To take out the sensor, one has to remove the electrical connector, the retaining clip, and the sensor, the O-ring is also disposed of. Installation is done in the reverse manner that it was done during removal, you have to use a new O-ring and then you end up refilling your cooling system. First for a 3.0L V6 engine, remove all the engine coolant. Remove the electrical connector from the ECT sensor and then remove the locking tab found at the bottom of the sensor, rotate the sensor anti-clockwise until it is unbolted from the coolant passage. Check on the sensor O-ring for any signs of cuts or signs of deterioration, if any then replace it. For fitting of the ECT sensor, it is simply screwed into the coolant passage and rotated clockwise until a locking tab fits in place, in the reverse of the disconnection process for the rest of the installation of the new parts. Last but not the least, the cooling system should be refilled.