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Coolant temperature sensor

Coolant temperature sensor



The temperature sensor is located in the intake manifold between the intake pipes of cylinders 3 and 4 and is in contact with the engine coolant. The sensor is of the NTC type.

The control module measures the coolant temperature by applying 5 V to the sensor from pin 78 via an integral 1 kohm resistor. The sensor is grounded via control module pin 71.

The voltage across the integral resistor in the control module is proportional to the temperature of the coolant.

This voltage is used to determine:


• the injection time for pre- injection

• the injection time for cold starting and warming-up enrichment

• engagement of closed loop

• idling speed.


Should the sensor fail to work or in the event of a break in the circuit (no continuity), the control module will use a default temperature of 60°C (140°F). At low ambient temperatures the engine may be reluctant to start.