Coolant Temperature Sensor (Cts)

CTS is a thermistor (a resistor that changes its resistance value based on temperature). A coolant temperature of -40°F (-40°C) produces a high resistance (100,000 ohms), while a coolant temperature of 266°F (130°C) produces a low resistance (70 ohms).

The ECM supplies a 5-volt reference signal to the CTS, through a resistor in the ECM and measures the return voltage. Voltage will be high when coolant temperature is low, and low when coolant temperature is hot. By measuring voltage, the ECM knows the engine coolant temperature. Engine coolant temperature affects the cold advance and glow plug systems.