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940 L4-2.3L SOHC VIN 88 B230F (1992)

Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Technical Service Bulletins > Page 5114

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Coolant Temperature Sensor/Switch (For Computer): Description and Operation

Coolant Temperature Sensor

PURPOSE

The coolant temperature sensor sends signals to the control module so that it can control injection time and idle speed in relation to engine
temperature.

DESIGN

The coolant temperature sensor is of the Negative Temperature Co-efficient (NTC) type.  This means the higher the coolant temperature, the lower
the sensor resistance.

OPERATION

The ECU applies a regulated constant voltage to the sensor, and monitors the voltage in the circuit. As temperature increases, sensor resistance
decreases, causing a decrease in the measured voltage of the circuit.

By monitoring the circuit voltage, the ECU can calculate the engine temperature, and adjust the air/fuel ratio and ignition timing to meet the
specific demands of the engine, at that temperature.

Powertrain Management > Computers and Control Systems > Coolant Temperature Sensor/Switch (For Computer) > Component Information > Technical Service Bulletins > Page 5114

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