Enhanced Testing

P0117 - Engine Coolant Temperature Circuit Low Input






General Description
The Engine Coolant Temperature (ECT) Sensor measures the temperature of engine coolant. The Engine Coolant Temperature (ECT) Sensor is located in the thermostat housing of the cylinder head. ECT Sensor is a thermistor (a variable resistor that changes along with ECT) in series with a fixed resistor in the Powertrain Control Module (ECM). The ECM applies 5 volts to the ECT sensor. The ECM monitors the voltage across the ECT sensor and converts it into a temperature reading. When the engine is cold the ECT sensor resistance is high, and when the engine is warm the ECT sensor 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 ECT sensor is used for Injection, ignition timing, idle speed and cooling fan control.

DTC Description
If ECT sensor's resistance is lower than 50 ohms, the ECM determines that a fault exists and a DTC is stored.

Detecting Condition and Specifications





Wiring Schematic





Signal Waveform