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Coolant temperature

Coolant temperature

The coolant temperature gauge gives the driver information on engine coolant temperature.

The main instrument unit receives information from the temperature sensor located in the left-hand end of the cylinder head where it is contact with the coolant. The temperature sensor is of NTC type. The main instrument unit measures the coolant temperature by applying 5 V to the sensor from pin 15 (K22) via an integrated 680 Ohm resistor. The sensor is grounded via main instrument unit pin 7 (K22). The voltage across the resistor in the main instrument unit is proportional to the coolant temperature. Information on the current coolant temperature is sent out on the bus.

The coolant temperature gauge's scale is divided into 5 fixed breakpoints. The main instrument unit is programmed to move the gauge needle to the fixed breakpoints at certain specific temperatures to give a steady reading at normal coolant temperatures.

The following breakpoints are programmed in the main instrument unit (factory setting):



Gauge needle:

Coolant temperature

-into "blue" zone

30°C (fixed value)

-out of "blue" zone

50°C

-into "horizontal" position

80°C

-out of "horizontal" position

115°C

-into "red" zone

129°C

-out of "red" zone

130°C (fixed value)



Diagnostics

A break/short circuit generates diagnostic trouble code B1715 and the coolant temperature sensor bottoms.