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.
2000 Pontiac Firefly (CANADA) L4-1.3LFACTORY OEM SERVICE PROCEDURE
Coolant Temperature Sensor/Switch (For Computer): Description and Operation
Engine Coolant Temperature (ECT) Sensor:
Engine Coolant Temperature (ECT) Sensor:
The Engine Coolant Temperature (ECT) sensor (1) is located in the thermostat housing near the rear ignition coil (2). The ECT sensor is a thermistor (a variable resistor that changes value when the temperature changes). The ECT sensor is connected in series with a fixed resistor in the Powertrain Control Module (PCM). The PCM applies 5 volts to the ECT sensor. The PCM monitors the voltage drop across the ECT sensor and converts the voltage reading into a temperature value. The ECT sensor voltage reading at the PCM will vary with the changes in the engine temperature.
Factory Service Tools
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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.