Functional description, see BMW Technology:
TIS -> Document -> SI Technology -> SBT Number 66 03 04 (086)
For the active cruise control (ACC), the gap to the vehicle ahead is measured by a radar sensor (ACC sensor). The pickup range lies between approx. 2 - 120 metres.
The active cruise control can be activated as of 30 kph.
The LDM control unit has the following tasks in the ACC function:
A precondition for the function of the ACC is that the engine / gearbox control and the DSC are operating without faults. For this reason, there is a continuous check as to whether the acceleration or braking requests are carried out without faults. In the event of a fault, the ACC is switched off.
Heavy soiling of the ACC sensor can mean that the function cannot be activated or the ACC is deactivated.
The ACC sensor must be adjusted horizontally and vertically in the installation location so that objects can be picked up without errors. This ACC sensor setting must be made on a special setting bay using special tools approved by BMW.
The service function ”Set ACC sensor” is available for the setting.
A poorly adjusted ACC sensor is detected. A fault is stored in the ACC fault code memory. The ACC cannot be activated until the sensor is correctly set.
If the ACC is active and the vehicle remains below the set required speed or does not accelerate, this can have the following causes:
The lens is heated to ensure the ACC is effective in winter and in poor weather conditions. This system is designed as a resistance heating system with the heating coil integrated in the plastic body of the lens. After the engine start, the lens heating in all ACC operating modes is switched on depending on the outside temperature.
To prevent the lens body from overheating, the lens heating system is switched off when the temperature inside the unit exceeds 50 °C. The temperature is measured by the interior temperature sensor of the ACC control unit. The ACC control unit is switched off at a system voltage > 16 V in order to protect the processor.
The lens heating is monitored by the ACC control unit for faults.