Steering Column Lock

The central electronic module (CEM), Driver information module (DIM) and steering column lock module (SCL) are part of the steering column lock function. The power supply to the Steering column lock module (SCL) is controlled by the Driver information module (DIM) via a relay in the Central electronic module (CEM). The steering column lock module (SCL) also receives commands from the central electronic module (CEM) to lock or unlock the steering column lock. The steering column lock only permits a function to be carried out when the vehicle is not in motion and the engine is off.

Whilst the vehicle is being driven, communication checks are carried out between the Driver information module (DIM) and the Central electronic module (CEM) to ensure that the Steering column lock is not activated by mistake. At the same time, the central electronic module (CEM) monitors the communication cable to the steering column lock module (SCL). If the central electronic module (CEM) detects that the steering column lock module (SCL) starts communicating when it should not be powered, the central electronic module (CEM) will display an warning message in the driver information module (DIM) and will attempt to disengage the steering column lock.

Unlocking 

When the central electronic module (CEM) receives a signal from the starter button (applies to vehicles with keyless function) or when the remote key is inserted in to the start control module (SCU) the key identity is checked, either via the keyless system or via the start control module (SCU). After approved validation of the remote key the central electronic module (CEM) transmits a command to the Driver information module (DIM) to power the Steering column lock module (SCL). The Driver information module (DIM) checks, using the signals from the Engine control module (ECM) and the Brake control module (BCM) that the engine is not running and the vehicle is stationary. If the conditions are met the Driver information module (DIM) activates power to the Steering column lock module (SCL). The Central electronic module (CEM) carries out the same checks as the Driver information module (DIM). If the Central electronic module (CEM) also considers the conditions to have been met the Central electronic module (CEM) gives an unlocking command to the Steering column lock module (SCL). The steering column lock module (SCL) then attempts to unlock the steering column lock. If everything is OK, the steering column lock module (SCL) transmits two signals back to the central electronic module (CEM). One signal indicates that the steering column lock module (SCL) has not detected any internal faults and is functioning as intended. The other signal indicates that the spring bolt has moved to the unlocked position. The central electronic module (CEM) will then store an internal value for successful unlocking and then continues with the checks for the immobilizer system.

If the steering column lock does not unlock the first time, the steering column lock module (SCL) will make a further two unlocking attempts. The power supply to the Steering column lock module (SCL) is switched off between each attempt. If these also fail, the steering column lock module (SCL) will transmit a message about the fault to the central electronic module (CEM). The central electronic module (CEM) will then store a diagnostic trouble code (DTC) and the checks for the immobilizer system will be cancelled. It will not then be possible to start the engine.

Locking 

The following applies to vehicles without the keyless locking system: 

The Central electronic module (CEM) receives a ground connection from the contact breaker in the Start control module (SCU) that indicates that the remote key has been pushed to its limit position when it is o be removed from the Start control module (SCU). When the signal is received, the Central electronic module (CEM) checks the signals on CAN that:

• the engine is switched off, from the Engine control module (ECM)
• the vehicle is stationary, from the Brake control module (BCM).

If the engine has been switched off and the vehicle is stationary, the Central electronic module (CEM) transmits a message to the Driver information module (DIM), to activate the power supply to the Steering column lock module (SCL). The Driver information module (DIM) then checks the signals on CAN, that the engine is switched off and that the vehicle is stationary. If this is the case the Driver information module (DIM) activates the power supply to the Steering column lock module (SCL), via a relay in the Central electronic module (CEM), and transmits an acknowledgment to the Central electronic module (CEM) via CAN stating that power is on. The Central electronic module (CEM) will then transmit a message to the Steering column lock module (SCL). The Steering column lock module (SCL) transmits a message back to the Central electronic module (CEM) stating whether locking was successful or not. The central electronic module (CEM) will store a diagnostic trouble code (DTC) if locking has failed after 3 attempts.

Locking 

The following applies to vehicles with the keyless locking system: 

After the ignition has been switched off and the driver's door opened, the Central electronic module (CEM) checks the signals on CAN that:

• the engine is switched off, from the Engine control module (ECM)
• the vehicle is stationary, from the Brake control module (BCM).

If the engine has been switched off and the vehicle is stationary, the Central electronic module (CEM) transmits a message to the Driver information module (DIM), to activate the power supply to the Steering column lock module (SCL). The Driver information module (DIM) then checks the signals on CAN, that the engine is switched off and that the vehicle is stationary. If this is the case the Driver information module (DIM) activates the power supply to the Steering column lock module (SCL), via a relay in the Central electronic module (CEM), and transmits an acknowledgment to the Central electronic module (CEM) via CAN stating that power is on. The Central electronic module (CEM) will then transmit a message to the Steering column lock module (SCL). The Steering column lock module (SCL) transmits a message back to the Central electronic module (CEM) stating whether locking was successful or not. The central electronic module (CEM) will store a diagnostic trouble code (DTC) if locking has failed after 3 attempts.