E90, E91 and E60, E61, E63, E64 from 09/2005
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The Servotronic valve is actuated directly by the AL control unit.
The signals and messages required for the Servotronic are as follows:
- Road speed from the DSC control unit via the PT-CAN
- Status of the engine from the DME control unit via the PT-CAN
- Terminal status of the CAS control unit via the K-CAN
The Servotronic valve is actuated only when terminal 15 is ON and the engine is running. When the speed signal is present the default value of the nominal current is taken from the characteristic map.
The current supply to the Servotronic valve is interrupted by the faults listed below. Under these circumstances, steering assistance is limited to a minimum:
- Speed signal from the DSC control unit incorrect or no speed signal
- Terminal status from CAS control unit via K-CAN incorrect or missing
- Line fault to the Servotronic valve (exception: short-circuit to positive)
In the event of a short-circuit to positive, the entire on-board network voltage is applied to the Servotronic valve. This means that the Servotronic valve is fully actuated. Under these circumstances steering assistance is increased to maximum.