9000 Aero L4-2290cc 2.3L DOHC Turbo EFI (1996)
Coolant Temperature Sensor/Switch (For Computer): Description and Operation
The temperature sensor is located in the intake manifold between the intake manifolds of cylinders 2 and 3 and is in contact with the engine coolant. The
sensor is of the NTC type.
The engine control module measures the coolant temperature by applying 5 V to the sensor from pin 68 via an integral 2.74 kohm resistor. The sensor is
grounded via pin 67 of the control module.
The ECM receives reference ground from the sensor ground lead to pin 66 to obtain a precise temperature measurement. The voltage across the resistor
in the ECM is proportional to the coolant temperature.
The voltage is used to determine fuel injection duration for pre-injection as well as for cold starting and producing a richer fuel/air mixture during the
warming-up period. Activation of closed loop and idling speed is also dependent on engine coolant temperature.
In the event of sensor failure or a break in the circuit, the engine control module will set a default temperature that is equivalent to the intake air
temperature on starting and then increased by 1°C (1.8°F) every 150th engine revolution.
