Diagnosis & Repair Procedure
NOTE:
Testing of ECT sensor system should be performed on a level road.
- Perform DTC CONFIRMATION TEST . If DTC P0116 is set, go to next step. If DTC P0116 is not set, problem is intermittent. System is okay at this time. See TROUBLE SHOOTING - NO CODES article.
- Ensure heater is off. Start engine and allow to reach normal operating temperature. Using scan tool, select ECT parameter. With engine at idle, observe scan tool parameter. If parameter reading varies about 1.8°F (or about 1°C) or more, go to next step. If parameter reading does not vary about 1.8°F (or about 1°C) or more, go to step 4.
- Check heater operation and coolant flow. If heater takes a long time to become effective, or coolant flows into radiator on cold start, check thermostat operation. Replace as necessary and go to DTC CONFIRMATION TEST . If thermostat operates properly, go to next step.
- Drain coolant. Disconnect ECT sensor connector. Remove ECT sensor from thermostat housing. Measure resistance between ECT sensor terminals while it is immersed in a container of water. Heat water slowly and ensure resistance changes as specified. See Fig 1. Replace ECT sensor as necessary. If resistance is as specified, check for high resistance or poor connection in ECT sensor circuit. Repair as necessary and go to DTC CONFIRMATION TEST . If ECT sensor circuit checks okay, replace PCM and go to DTC CONFIRMATION TEST .