Code 14, Coolant Temp. Circuit Low Temp. Indicated

The coolant temperature sensor uses a thermistor to control signal voltage to ECM. ECM applies voltage on the Gray/White wire to sensor. When engine is cold, thermistor resistance is high. ECM will senses high signal voltage.

As engine warms, thermistor resistance is less. ECM will sense low signal voltage. When engine reaches normal operating temperature of approximately 176-203°F (80-95°C), signal voltage will be approximately 1.5-2.0 volts at ECM.

NOTE: Test numbers refer to test numbers on diagnostic chart.

Code 14 will be set if signal voltage indicates coolant temperature is less than -54°F (-48°C) for 3 seconds.
This simulates a Code 15. If ECM senses low signal voltage and sets a Code 15, ECM and wiring are okay. If Code 14 is set again, problem is an open Gray/White or Lt. Green/Black wire, poor connection at ECM, or faulty ECM.