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

The coolant temperature sensor uses a thermistor to control signal voltage to the ECM. The ECM applies voltage on circuit No. 410 to coolant sensor. When engine is cold, sensor resistance is high. This means ECM sees high signal voltage. When engine warms, sensor resistance lowers and voltage drops. With engine at normal operating temperature, 176-203°F (80-95°C), voltage measures approximately 1.5-2.0 volts at the ECM.

1. If signal voltage indicates a coolant temperature less than -47°F (44°C) for 20 seconds, this will set a Code 14.
2. This simulates a Code 15. If the ECM sees the low signal and sets a Code 15, the ECM and wiring are okay. If Code 14 repeats, the problem is an open in circuits No. 410 and 452 , a poor connection at ECM or sensor, or a faulty ECM.