Code 14, Coolant Temp Sensor CKT/Low Temp Indicated

The Coolant Temperature Sensor (CTS) uses a thermistor to control signal voltage to ECM. ECM applies voltage on Red/Yellow wire to coolant sensor. When engine is cold, sensor resistance is high. ECM will sense high signal voltage. As engine warms, sensor resistance lowers, and voltage drops. With engine at normal operating temperature, 176-203°F (80-95°C), voltage will be about 1.5-2.0 volts at the ECM.

1. If signal voltage indicates coolant temperature is less than -48°F (44°C) for 5 seconds, Code 14 will set.
2. This simulates Code 15. If ECM senses low signal and sets a Code 15, ECM and wiring are okay. If Code 14 repeats, problem is open in Red/Yellow or Gray/Yellow wire, poor connection at ECM or sensor, or faulty ECM.