P0117-Engine Coolant Temperature Sensor Circuit Low: Notes

Fig 1: AAT, ECT & IAT Sensors Circuit Schematic

Courtesy of CHRYSLER LLC

For a complete wiring diagram, refer to appropriate SYSTEM WIRING DIAGRAMS article  .

Theory of operation 

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 supplies a ground to the low reference circuit.