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 is a thermistor (resistance changes as engine coolant temperature changes). ECM supplies a 5-volt reference voltage to ECT sensor. As temperature changes, ECT sensor resistance changes, which changes voltage.
As coolant temperature decreases, ECT sensor resistance increases. As coolant temperature increases, ECT sensor resistance decreases. ECM monitors voltage input from ECT sensor and converts it into a temperature value. DTC will set when temperature does not reach 99°F (37°C) within a specified time (varies with engine starting temperature). ECT signal is continuously checked when ignition is on.
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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.