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.
1998 Oldsmobile Aurora V8-4.0L VIN CFACTORY OEM SERVICE PROCEDURE
Engine Coolant Temperature (ECT) Sensor
Voltage Versus Temperature Chart:
DESCRIPTION
The ECT sensor is a thermistor (a resistor that changes value due to temperature) mounted in the engine coolant flow.
OPERATION
High coolant temperatures result in low resistance and low temperatures result in high resistance. The PCM provides a 5 volt reference signal and a ground to the ECT sensor, and it measures the voltage signal as it changes due to the sensors resistance. A high coolant temperature will result in low signal voltage (near 0 volt) and low coolant temperature will result in high signal voltage (near 5 volts).
The ECT sensor circuit uses two different temperature sensing circuits for two temperature ranges - below 50°C (122°F) and above 50°C (122°F). The PCM will shift between a high resistance circuit for low temperatures and a low resistance circuit for high temperatures.
Factory Service Tools
Use the Manual With the Right Hardware
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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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