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.
1991 Ford Probe V6-182 3.0LFACTORY OEM SERVICE PROCEDURE
Coolant Temperature Sensor/Switch (For Computer): Description and Operation
Engine Coolant Temperature Sensor:
The Engine Coolant Temperature (ECT) sensor is threaded into a coolant passage with the sensing bulb extending into the coolant.
The ECT sensor is a negative temperature coefficient sensor, meaning that as the temperature of the sensor increases, the resistance will decrease. As the resistance value changes, the signal sensed by the Electronic Control Assembly (ECA) also changes. The ECA reads the varying sensor resistance and determines the engine operating temperature, using this information to optimize the air/fuel mixture and ignition timing.
The ECT sensor will also set a fault code when the ECA determines the output signal to be out of the normal operating range.
ECT resistances:
-40° 269 K ohms
32° 95 K ohms
77° 29 K ohms
248° 1.2 K ohms
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.