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
The DTC P0115 Engine Coolant Temperature (ECT) sensor circuit diagnostic detects an out of range sensor signal. ECT sensor is a thermistor. A thermistor is a resistor whose value varies with temperature. Resistance of ECT sensor is high when coolant temperature is cold, and resistance is low when coolant temperature is warm. ECT sensor is wired in series with a fixed resistor in the Powertrain Control Module (PCM). PCM applies 5 volts to the ECT sensor. PCM monitors voltage across ECT sensor and converts voltage into a temperature reading. Voltage measured by PCM will be high when coolant temperature is cold, and low when coolant temperature is warm. See IAT RESISTANCE/SIGNAL VOLTAGE table.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.