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.
Engine Coolant Temperature Sensor
The Engine Coolant Temperature (ECT) sensor is a thermistor (temperature sensitive resistor). An engine coolant temperature of -40°F (-40°C) produces a high resistance (100 k/ohms), while an engine coolant temperature of 266°F (130°C) produces a low resistance (70 ohms).
PCM supplies a 5-volt reference signal through an internal resistor to ECT sensor and measures return voltage. Voltage is high when coolant temperature is low, and low when coolant temperature is hot. By measuring voltage, PCM can determine engine coolant temperature. Engine coolant temperature affects injector timing and glow plug system.
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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.