Coolant Temperature Sensor

1. Powertrain Control Module (PCM)
2. Throttle Position (TP) sensor
3. Mass Air Flow (MAF) sensor
4. Intake Air Temperature (IAT) sensor
5. Idle Air Control (IAC) valve
6. Engine Coolant Temperature (ECT) sensor
7. Heated Oxygen Sensor (HO2S)
8. Camshaft Position (CMP) sensor
9. Knock Sensor (KS)
10. Vehicle Speed Sensor (VSS)
11. Crankshaft Position (CKP) sensor
12. Fuel Injector
13. Coolant Temperature Sensor (CTS)
14. Exhaust Gas Recirculation (EGR)
15. Manifold Absolute Pressure (MAP)

Source: FreeAutoMechanic.com/car-engine-sensors.html

Coolant Temperature Sensor (CTS)

Measures the temperature in the cooling system, so the computer may make adjustments based on the engine's operating temperature. Can also control the dashboard warning light.

ECT Sensor - Electronic Coolant Temperature

The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. When the engine coolant temperature is low, the sensor resistance is high. When the engine coolant temperature is high, the sensor resistance is low. The Engine Coolant Temperature Sensor (ECT) input to the PCM is a primary input for calculation strategies, fuel delivery control and spark timing. The ECT is also used to determine loop status timer requirements (inside of PCM) and to support cooling fan operation. ECT failures can cause excessive rich conditions, increased injector pulse-width and retarded spark timing.