The Monte Carlo's engine coolant temperature, or ECT, sensor measures the temperature of the engine coolant and sends a signal to the powertrain control module, or PCM. This is a bi-directional sensor, in that the PCM sends 5 volts to the sensor. If the coolant temperature is low, the resistance to the voltage is high. If the coolant temperature is high, the resistance to the voltage is low. The computer uses this information to control several things in the engine, including timing.
Locate the temperature sensor on the intake manifold, near the thermostat housing.
Unplug the sensor's wiring harness connector by prying the tangs on the side of the plug away from the plug and pulling it off the sensor. Fit the appropriate wrench onto the sensor's hexagon-shaped body. Turn the sensor counterclockwise to remove it.
Wrap the threads with white pipe tape. Screw the sensor into the intake manifold by hand as far as it will go. Tighten it firmly, using the wrench, but do not overtighten the sensor. Plug in the wiring harness connector.
