Code EO14, Coolant Sensor Temperature Too High
The coolant temperature sensor is a thermistor that changes in resistance with temperature. When the engine is cold, the resistance of the sensor is high; as the engine warms, the resistance of the sensor decreases.
The ECM applies a 5-volt signal at C10. When the engine is cold, (resistance high), the ECM will see a high voltage at C10. As the engine warms, (resistance decreases), the voltage at C10 will decrease. At normal engine operating temperature, the ECM will see 1-1.5 volts at terminal C10.
Coolant temperature is one of the inputs used to control: Fuel delivery, engine spark timing (EST), knock control (ESC), idle speed (IAC), converter clutch (TCC), canister purge (CCP) and EGR.
Code EO14 will set if: Coolant temperature is above 285°F (140°C) for 4 seconds, or engine run time is longer than 20 seconds.
- Validate problem exists. If no problems exist, check for loose connections. Engine must be cool for reliable diagnosis. Make sure engine is not having an overheating problem.
- Disconnect coolant sensor. Display going to -38°C or colder indicates a faulty coolant sensor. If display does not change, circuit 410 has a possible short to ground, or the ECM is malfunctioning.
- Checking voltage at terminal "B" of coolant sensor connector will indicate that circuit 410 is shorted to ground if there is no reference voltage. Having reference voltage at terminal "B" would indicate a malfunction with the ECM.