Diagnosis & Repair Procedure
NOTE:
Testing of ECT sensor system should be performed on a level road.
- If engine system check has been performed, go to next step. If engine system check has not been performed, go to A4: ENGINE SYSTEM CHECK under SYSTEM TESTS.
- Ensure heater is off. Start engine and allow to reach normal operating temperature. Using scan tool, observe 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 (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. If problem is found, repair or replace as necessary. After repair, repeat DTC CONFIRMATION TEST . If thermostat operates properly, go to next step.
- Turn ignition off. Disconnect ECT sensor No. 1 3-pin harness connector. ECT sensor is located in thermostat housing. See Fig 1 . 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 2 . If ECT sensor resistance does not changes as specified, replace sensor. After repair, repeat DTC CONFIRMATION TEST . If resistance is as specified, go to next step.
- Check for high resistance or poor connection in ECT sensor circuit. If problem is found, repair as necessary. If ECT sensor circuit checks okay, substitute a known good ECM, and repeat DTC CONFIRMATION TEST . If DTC resets, go to next step. If DTC does not reset, testing is complete.