Diagnostic Aids

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Test the ECT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor can result in a DTC or a driveability condition. Refer to Temperature Versus Resistance .
If the vehicle has sat overnight, the IAT sensor and the ECT sensor values should display within 3°C (5°F).
After starting a cold engine, the ECT sensor temperature should rise steadily, then stabilize after the thermostat opens.
High resistance on either the ECT sensor signal circuit or the ECT sensor low reference circuit could set a DTC.