Remove the engine cover and drain the engine coolant; however, it is possible to replace the sensor without draining the coolant, though some coolant may leak from the crossover when the ECT sensor is removed, so install the new sensor quickly. For four-cylinder models, the ECT sensor is located at the rear of the engine near the transaxle end at the thermostat housing, so disconnect the electrical connector from the ECT sensor. In 2002 and 2003 (3.0L) V6 models, the ECT sensor is found on the coolant crossover at the left end of the engine between the cylinder heads; remove the battery, take off the cover from the fuse block, disconnect the power steering wire and the positive battery cable from the B+ terminal, disconnect all harnesses from the battery cooling box, loosen the fuse block connector mounting bolts, move the fuse block from its retainer, disconnect the wiring harness supplying the front lights, and remove the battery cooling box before disconnecting the electrical connector from the ECT sensor. For 2004 and later (3.5L) V6 models, the ECT sensor is mounted at the left side of the front cylinder head next to the thermostat housing, so disconnect the electrical connector from the ECT sensor. Unscrew the ECT sensor with a wrench, taking care to handle it gently if planning to reuse it, as damage will affect the PGM-FI system's operation. When installing the ECT sensor, apply sealant to the threads if it does not use an O-ring, and always remove and discard the old O-ring, installing a new one regardless of whether the old sensor is reused or a new one is installed. Finally, installation is the reverse of removal, ensuring the ECT sensor is tightened, and refill the cooling system or check the coolant level if it was not drained, adding as necessary.