850 L5-2.4L VIN 55 B5254S (1993)
Coolant Temperature Sensor/Switch (For Computer): Description and Operation
ENGINE COOLANT TEMPERATURE SENSOR
The Engine Coolant Temperature (ECT) sensor (7/16) is common to the MFI system, DI (distributor ignition) system and combined instrument panel.
The signal is used by:
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MFI module (4/45), to extend the opening period of the injectors (8/6-8/10) when the engine is started from cold and normal working temperature
has not yet been reached.
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ICM (4/10) to
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operate the engine cooling fan (6/29);
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switch out the A/C compressor (8/3) temporarily when the engine temperature is high;
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advance the timing when there is a risk of overheating;
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disconnect the Knock Sensor (7/23 and 7/24) when the engine is cold;
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Combined instrument (5/1), for engine temperature indication.
The MFI module converts the analogue signal from the ECT into a digital signal (1) for transmission to the TCM and combined instrument. The
digital signal consists of a square-wave pulse with a pulse length proportional to the coolant temperature.
ECT Sensor - Design
The sensor is mounted in the thermostat housing. The unit consists of a brass body enclosing a temperature sensitive NTC resistance and an integral
lead with a sealed, 2-pin connector to simplify accessibility.
The accuracy of the information is maintained by converting the sensor signal to a digital signal.