DTC P0117-00: Engine Coolant Temperature Circuit Low Input: General Description

The Engine Coolant Temperature Sensor (ECTS) measures the temperature of engine coolant. The Engine Coolant Temperature Sensor (ECTS) is located near the thermostat housing of the cylinder head. The Engine Coolant Temperature Sensor (ECTS) is a thermistor (A Variable Resistor that changes along with ECT) in series with a fixed resistor in the ECM. The ECM applies 5 volts to the Engine Coolant Temperature Sensor (ECTS). The ECM monitors the voltage across the ECTS and converts it into a temperature reading. When the engine is cold the ECTS resistance is high, and when the engine is warm the Engine Coolant Temperature Sensor (ECTS) resistance is low. Therefore, when the engine is cold the ECM will receive a high voltage input, and when the engine is warm the ECM will receive a low voltage input. The Signal from the Engine Coolant Temperature Sensor (ECTS) is used for Injection control, ignition timing, idle speed and cooling fan control.