Code 14: Coolant Sensor Temp To High: Notes

The coolant temperature sensor uses a thermistor to control the signal voltage to the ECM. The ECM applies a voltage on circuit No. 410 to the sensor. When the engine is cold, the sensor (thermistor) resistance is high, therefore the ECM will see high signal voltage.

As the engine warms, the sensor resistance becomes less, and the voltage drops. At normal engine operating temperature, the voltage will measure about 1.5-2.0 volts at the ECM terminal No. E16.

1. Checks to see if code was set as result of hard failure or intermittent condition. Code 14 will set if the following conditions occur:
   • Engine has been running for more than 10 seconds.
   • Signal voltage indicates a coolant temperature above 275°F (135°C) for 3 seconds.
2. This test simulates conditions for a Code 15. If the ECM recognizes the open circuit (high voltage), and displays a low temperature, the ECM and wiring are okay.