Code 14, Coolant Temperature Sensor (Cts) Circuit High Temperature Indicated: Notes

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

As engine warms, thermistor resistance is less. This means the ECM will see 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 the ECM.

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