If you unplug the ECT, voltage output is 0VDC to the signal return path to the ECU pin 46. Low voltage out of the ECT correlates to warm engine temperature. The TPS, ACT, ECT and EGR outputs all go through the white salt and pepper shaker pin 1, which is the signal return to ECU Pin 46. The way I understand this is all 4 sensors have their output voltages summed together and the total voltage signal goes to ECU pin 46.