P0118 - Engine Coolant Temperature Sensor Circuit High: Notes

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.

• >>When Monitored:<< With the ignition on. Battery voltage greater than 10.4 Volts.
• >>Set Condition:<< The Powertrain Control Module (PCM) detects that the Engine Coolant Temperature Sensor input voltage is above the maximum acceptable value. One Trip Fault. Three good trips to turn off the MIL. The MIL and ETC light will illuminate if equipped.

Possible Causes
(K2) ECT SIGNAL CIRCUIT SHORTED TO VOLTAGE
(K2) ECT SIGNAL CIRCUIT OPEN
(K900) SENSOR GROUND CIRCUIT OPEN
ENGINE COOLANT TEMPERATURE (ECT) SENSOR
POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Refer to Pre-Diagnostic Troubleshooting Procedure .