Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit Description
Engine Coolant Temperature (ECT) sensor contains a thermistor which changes resistance based on temperature. ECT sensor is located in coolant crossover pipe at center rear of engine. Sensor has a signal and ground circuit. ECM applies about 5 volts on signal circuit of sensor. ECM monitors changes in voltage caused by changes in resistance of sensor to determine engine coolant temperature.
When engine coolant is cold, sensor resistance is high. ECM will sense a high signal voltage (low temperature). When engine coolant is warm, sensor resistance is low. ECM will sense a low signal voltage (high temperature). When ECT signal voltage indicates an engine coolant temperature greater than 282°F (139°C) or less than -45°F (-43°C), DTC P0115 will set. For duplication of DTC, ensure engine is running.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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