Code 14, Coolant Temp Sensor (Cts) CKT, Low Temp Indicated: Notes

The CTS uses a thermistor to control signal voltage to ECM. ECM applies voltage on Gray/Black wire to sensor. When engine is cold, thermistor resistance is high. Thus, ECM will sense high signal voltage.

As engine warms up, 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. Coolant temperature is one of the inputs used by ECM to control fuel delivery, Electronic Spark Control (EST) and Idle Air Control (IAC).

1. Checks if code is due to a hard failure or intermittent condition. Code 14 is set when signal voltage indicates coolant temperature is less than -22°F (-30°C) for 2 minutes.
2. This simulates conditions for Code 14 (high temperature indicated). If ECM senses grounded circuit (low voltage) and displays high coolant temperature, ECM and wiring are okay.
3. This determines if ECM and/or wiring is faulty.