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:

^ 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.

^ ICM (4/10) to
- operate the engine cooling fan (6/29);
- switch out the A/C compressor (8/3) temporarily when the engine temperature is high;
- advance the timing when there is a risk of overheating;
- disconnect the Knock Sensor (7/23 and 7/24) when the engine is cold;

^ 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.