DSC control unit
Like the hydraulic modulator, the DSC control unit on the F01/F02 is also based on the one used on the E70/E71.
Specifically, the following special features and differences should be noted:
- FlexRay connection
- Wiring of the new DTC button
- Wheel-speed signals for electromechanical parking brake, Car Access System and Telematic Control Unit
| Index | Explanation |
|---|---|
| 1 | DSC control unit |
| 2 | FlexRay input with terminal resistor |
| 3 | DF_TCU_L, front left wheel-speed signal for Telematic Control Unit (TCU) |
| 4 | DF_TCU_R, front right wheel-speed signal for TCU |
| 5 | WUP, wake-up line |
| 6 | DFA_EMF, wheel-speed signal for Car Access System (CAS) |
| 7 | DFA_EMF, wheel-speed signal for electromechanical parking brake (EMF) |
| 8 | Power supply for DSC module (Terminal 30F) |
| 9 | Power supply for valves (Terminal 30) |
| 10 | Power supply for pump motor (Terminal 30) |
| 11 | Ground for DSC module |
| 12 | Ground for valves and pump motor |
The DSC control unit on the F01/F02 is connected to the FlexRay and not, as on previous vehicles, to the PT-CAN and F-CAN.
The FlexRay is brought to the DSC control unit (from the ZGM) and ends there. The DSC control unit is thus the terminal node of the FlexRay. Accordingly, it contains a terminal resistor for the FlexRay.
On previous vehicles, the DTC button was electrically analyzed by the IHKA control unit, for instance (E70/E71). On those vehicles, the button operation signal is transmitted via bus systems to the DSC control unit.
The new DTC button on the F01/F02 is connected to the ICM control unit instead. The DTC button and the associated function is part of the "dynamic handling control" function on the F01/F02. As that, in turn, is computed on the ICM control unit, the DTC button has been connected to the ICM control unit. The ICM control unit then signals the appropriate vehicle handling mode via the FlexRay. The DSC control unit analyses the signalled mode and adapts its function accordingly.
For the EMF and CAS control units, the information about vehicle standstill is of particular importance. For those two systems, the DSC control unit provides the DFA_EMF signal. It is a calculated signal computed from the speeds of the two rear wheels. It is transmitted as a pulse-width modulated signal on a dedicated line to the EMF and CAS control units.
If there is a Telematic Control Unit (TCU) fitted on the vehicle but no navigation system, the TCU control unit has to take on the task of determining vehicle location. That is necessary for the manual and automatic emergency call functions. The signals from the GPS aerial are insufficient for that purpose as it has to be possible to determine the vehicle's location even if the GPS signals are temporarily unavailable. In that case, the TCU control unit uses the speed signals from the two front wheels to calculate the road speed and changes of direction when cornering. The wheel-speed signals are provided by the DSC control unit and transmitted to the TCU control unit by a directly wired connection (DF_TCU_L and DF_TCU_R).
The power supply for the DSC unit is split into three: control unit, valves and pump motor are supplied by separate leads. That prevents interference from the load circuits (inductive loads) being transferred to the electronic circuitry.
The DSC control unit is also connected to the wake-up line. The wake-up line is used to wake up the DSC control unit.