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DTC P0116: Engine Coolant Temperature (ECT) Circuit Range/Performance Problem

  1. Connect scan tool to Data Link Connector (DLC). Start engine. Select ECT parameter. Run engine until operating temperature is reached with heater blower switch off. With engine at idle, observe scan tool display. If display reading varies about 2°F (1°C) or more, go to next step. If display reading does not vary about 2°F (1°C) or more, go to step  3 .
  2. Check thermostat operation. If heater takes a long time to become effective, or coolant flows into radiator on cold start, remove thermostat for inspection. Replace as necessary and retest system. If thermostat operates properly, go to next step.
  3. Drain coolant. Disconnect ECT sensor harness connector and remove sensor from engine. Measure resistance between ECT sensor terminals while immersed in a container of water. Heat water slowly and ensure resistance changes as specified. Go to ENGINE COOLANT TEMPERATURE (ECT) SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article. If resistance is not as specified, replace ECT sensor. If resistance is as specified, go to next step.
  4. Check for high resistance or poor connection in ECT sensor circuit. Repair as necessary. If ECT circuit checks okay, replace PCM.
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