9-3 SE Hatchback (9400) L4-2.0L Turbo (B205) HO (2000)
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On oars with Trionic T5 or Motronic, the MIU has its own coolant temperature sensor.
Cars with the Trionic T7 have only one engine coolant temperature sensor. Since the engine control module is connected to a bus, the temperature of the
coolant is continuously available to all systems. That is why only one engine coolant temperature sensor is needed.
On diesel cars the EDC 15 has an engine coolant temperature sensor. Since the engine control module is connected to a bus, the temperature of the
coolant is continuously available to all systems. That is why only one engine coolant temperature sensor is needed on cars with a diesel engine.
The coolant temperature is used by the DICE for controlling the radiator fans (see illustration), by the MIU for controlling the temperature gauge, and by
the ACC for controlling ventilation fan speed and air distribution when starting from cold. Basically, it could be said that the control modules connected
to a bus are like one big control module with a number of sensors and a number of actuators. Bus communication may be regarded as internal control
module communication.
This means that an overall view of the car is essential when carrying out fault diagnosis. A malfunction need not necessarily be caused by a fault in the
system where it occurs but may very well be caused by a defective sensor in another system.
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