Q: How do you remove and install the ECT sensor for Cadillac DeVille and DTS?
A: You can find the ECT sensor behind the engine, the edge facing the firewall and below the EGR Valve. The first step of removing the ECT sensor is unplugging its cable from the negative battery cable. It is important to empty part of engine coolant before taking out ECT sensor from the vehicle, as it helps in reducing cooling loss. Then disconnect electrical connector from ECT sensor and unscrew sensor from thermostat housing. Prepare that some coolant will come out when you remove this sensor if you never removed any coolant. Prior to fitting new ECT sensor wrap its threads with Teflon sealing tape to prevent leakages and corrosion of threads. It's a good idea if you have an old thread sealant on or rewrap threads with fresh teflon tape even if you plan on putting back your old ECT sensor. Fasten down and torque up until it gets tightened. Installation is otherwise a reverse of removal. Finally, check for necessary coolant level in relation to engine temperature. Begin running it until it reaches operating temperature as usual and then inspect for leaks where there might be some antifreeze dripping off somewhere at this point in time or is it just because of other reasons? Let's go back to expansion tank after engine has warmed up then cooled down.