Code 14, ECT Circuit High/Low Temperature Indicated: Notes

Engine Coolant Temperature (ECT) sensor uses a thermistor to control signal voltage to ECM. ECM applies voltage on Gray/Black wire to sensor. When engine is cold, sensor (thermistor) resistance is high. ECM will then sense high signal voltage.

As engine warms, sensor (thermistor) resistance decreases and ECM senses low signal voltage. When engine reaches normal operating temperature, signal voltage will be approximately 1.5-2.0 volts at ECM terminal C10. Engine coolant temperature is one of the inputs used by ECM to control fuel delivery, Ignition Control (IC) and Idle Air Control (IAC).

1. Checks if code is due to a hard failure or intermittent condition. Code 14 will set if signal voltage indicates engine coolant temperature greater than 412°F (213°C) for 3 seconds. Code 14 will also set if engine has been running for at least 2 minutes and engine coolant temperature is less than -35°F (-37°C).
2. Simulates conditions for Code 14 (low temperature indicated). If ECM senses open circuit (high voltage) and displays low coolant temperature, ECM and wiring are okay.
3. Determines if ECM and/or wiring is faulty.