Displaying Engine Coolant Temperature

Networking:

Signal flow
- The coolant temperature sensor (B11/4) changes its resistance depending on coolant temperature. (The sensor is an NTC resistance, i.e. the resistance decreases as temperature increases.)
- The resistance of the coolant temperature sensor (B11/4) is read in by the injection system control module (N3).
- The injection system control module (N3) converts the resistance values of the coolant temperature sensor (B11/4) into a temperature value.
- This temperature value is sent to the CAN/engine compartment by the injection system control module (N3).
- The instrument cluster (A1) reads in this temperature value from the CAN/engine compartment and actuates the ECT gauge (A1p1) accordingly. If necessary a warning message also appears in the multifunction display (A1p13). The ECT gauge (A1p1) is driven by a stepper motor.

Display of coolant temperature
- This display is a plateau display, i.e. the pointer stays on 95 °C at temperatures between 95 °C and 115 °C. Temperatures in this range are not critical. The correct temperature is displayed again for temperatures of 116°C and over. This prevents the driver being unnecessarily disturbed by the display, e.g. at high outside temperature.
- The warning range starts at 128 °C. From 128 °C the coolant thermometer symbol and the warning message "COOLANT STOP, SWITCH OFF ENGINE" is displayed in the multifunction display (A1p13). In addition a warning tone sounds.


NOTE: If the engine fan is defective, the plateau characteristic is exited and values between 95 °C and 115 °C are also displayed.