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

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1994 GMC Yukon, 1994 GMC Suburban, 1994 GMC Pickup, 1994 GMC Cab & Chassis, and 1994 GMC C3500 HD. However, it is still accessible from the selected car via links, so may be relevant.

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 the ECT signal circuit is open or for a faulty PCM.