Astra L4-1.8L (2009)
Body Control Systems: Description and Operation
Body Control System Description and Operation (Steering Column Control Module)
Body Control System Description and Operation (Steering Column Control Module)
SCCM
The steering column control module (SCCM) is the module on the steering column which, amongst other things, contains the ignition lock and the turn
signal and wiper switches. It combines the following sub-systems (some of which are optional).
Immobilizer, steering wheel controls, transponder aerial, ignition lock, turn signal stalk, main/dipped beam stalk, cruise control stalk, Info Display
buttons, windscreen wiper stalk, radio receiver for the key remote control, steering angle sensor, horn button, PEPS start button (passive entry passive
start system) and ESCL (electric steering column lock). The SCCM has been developed to reduce the complexity of the wiring and reduce the weight of
the steering column.
SCCM Control Unit
The steering column control module (SCCM) control unit has two CAN interfaces, one to the low-speed CAN bus and one to the high-speed CAN bus. It
is used as the interface between the high-speed bus and the low-speed bus to exchange information between the CAN buses. All components of the
SCCM, except the ignition key with its RF receiver/transmitter (transponder), are directly connected to the SCCM control unit (plug connection) and
therefore require no additional wiring.
Voltage Management, Voltage Supply, Ignition Lock
The SCCM control unit is responsible for voltage management within the vehicle. It is responsible for decoding the ignition lock information (ignition
key position) and for forwarding this information as CAN information to the rest of the vehicle. In addition, the SCCM actuates, by hard wiring, two
power supply relays in the UEC and REC. The ACC (ignition lock position 1) signal is also transmitted by hard wire to the ECM to power it up more
quickly. The engine will fire more quickly as a result.
Bus Interface to the High-Speed CAN (HS CAN) and Low-Speed CAN (LS CAN)
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The SCCM has two CAN interfaces for data communication.
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High-speed CAN for engine systems, drive train systems, immobilizer, etc.
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Single wire low-speed CAN for body systems.
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Interface between HS CAN and LS CAN.
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The SCCM is the interface (transfer point) between the low-speed bus and the high-speed bus. Selected bus messages are transferred from the
low-speed bus to the high-speed bus and vice versa.
Diagnostics Interface
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The SCCM control unit has a CAN diagnostics interface to the HS CAN and the LS CAN. The HS and LS bus lines are looped through the SCCM
to the diagnostics plug. Warning: If the SCCM plug is disconnected, the connection between the diagnostics plug and the HS and LS bus is
interrupted.
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To avoid damage to control units in the CAN network by external voltage shorts or ground shorts, the SCCM control unit has an internal
protective circuit both for the HS CAN and the LS CAN. Diagnosis is also carried out by means of the CAN bus.
Dimming the Steering Wheel Controls Illumination
The buttons for the steering wheel controls are illuminated. This illumination is dimmed in response to information which is transmitted by the IPC to the
SCCM via the LS CAN.
Turn Signals Function
The SCCM control unit records 4 positions of the turn signal stalk in digital form. The turn signal stalk no longer engages mechanically and instead
returns to its initial position, even when the turn signals are switched on. They are switched off either by the steering angle sensor or by moving the stalk
in the opposite direction. This information is transmitted by the SCCM control unit via the LS CAN to the REC which then specifies the flash frequency
and the duty factor.
Cruise Control Function
The SCCM control unit records the 3 positions of the cruise control switch in digital form. This information is transmitted by the SCCM control unit to
the engine control module (ECM) control unit via the HS CAN.
Windscreen Wiper Function
The SCCM control unit records the 6 positions of the windscreen wiper stalk in digital form. This information is transmitted by the SCCM control unit to
the UEC control unit via the LS CAN. The wiper stalk no longer engages mechanically; instead, it returns to its initial position even when the wipers are
