Diagnostic Aids

Test the ECT and the IAT 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 - Engine Coolant Temperature Sensor and Temperature Versus Resistance - Intake Air Temperature Sensor .
If the vehicle has sat overnight, the scan tool IAT sensor and ECT sensor parameters should display within 3°C (5°F) of each other.
After starting a cold engine, the ECT sensor temperature should rise steadily, then stabilize after the thermostat opens.
High resistance in the circuits of either the ECT or IAT sensor could set a DTC.
A short to ground or voltage through a conductive material or fluid could set this DTC. Inspect the ECT sensor for evidence of engine coolant leaking into the connector body.