The engine coolant temperature (ECT) sensor is a variable resistor, that measures the temperature of the engine coolant. The powertrain control module (PCM) supplies 5 volts to the ECT signal circuit and a ground for the ECT low reference circuit.


When the ECT is cold, the sensor resistance is high. When the ECT increases, the sensor resistance decreases. With high sensor resistance, the PCM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the ECT signal circuit. If the PCM detects an excessively low ECT signal voltage, which is a high temperature indication, DTC P0117 sets.


If the PCM detects an excessively high ECT signal voltage, which is a low temperature indication, DTC P0118 sets.

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  • Guest - Nicsha

    My suv crank no start the replace replace spark plugs add gas still sound floodef are stalling

  • Guest - Guest

    Resistance goes up as temp goes up not down. P0117 is low temp, P0118 is high temp.