Coolant Temperature Sensor (CTS)
The coolant sensor is a thermistor (a resistor which changes value based on temperature) mounted in engine coolant stream. See Fig 1 . The coolant sensor is a "two wire" sensor with a reference signal voltage from PCM to sensor pin B and a sensor reference ground from PCM to sensor pin A. Low coolant temperature produces a high resistance (100,000 ohms at -40°C/-40°F) while high temperature causes low resistance (70 ohms at 130°C/266°F).
The PCM supplies 5 volt signal to coolant sensor through a resistor in PCM and measures signal voltage. The voltage will be high when engine is cold (sensor high resistance), and low when engine is hot (sensor is low resistance).
The sensor provides coolant temperature information to PCM for fuel enrichment, ignition timing, canister purge control, idle speed control, and "Closed Loop" fuel control. A failure in coolant sensor circuit should set either a Code E014 or Code E015.