Code 14: Cts Circuit-High Temp Indicated (Turbo): Notes

Coolant temperature sensor uses a thermistor to control signal voltage to the ECM. The ECM applies voltage on Gray/Black wire to the sensor. When engine is cold, thermistor resistance is high and ECM will see a high signal voltage.

As engine warms, thermistor resistance is less and ECM will see a 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 an input used by the ECM to control fuel delivery, Electronic Spark Control (EST) and idle air control.

1. This determines if code set because of a hard failure or an intermittent condition. Code 14 sets if signal voltage indicates a coolant temperature greater than 293°F (145°C) for 2 minutes.
2. This simulates conditions for Code 15. If ECM sees open circuit (high voltage) and displays low coolant temperature, ECM and wiring are okay.