DTC 15, ECT Sensor Circuit High (Low Temperature Indicated): Notes

Engine Coolant Temperature (ECT) sensor is a thermistor that controls signal voltage to PCM. When engine is cold, sensor resistance is high, and PCM will sense a high signal voltage. As engine warms, sensor resistance becomes less and voltage drops. DTC 15 will set when engine coolant temperature is less than -33°F (-36°C) and engine has been running for at least 8 minutes.

PCM will default to a engine coolant temperature of 64°F (18°C) and increase idle speed.

NOTE: Test numbers refer to numbers on diagnostic chart.

This step determines if DTC 15 is the result of a hard failure or an intermittent condition.
This step determines if ECT signal circuit is open or for a faulty PCM.