Control of the electric steering interlock
During the unlocking procedure, an authentication procedure is run between the Car Access System (CAS) and the electric steering lock. The electric steering lock may only commence unlocking after a positive result in the authentication procedure. For safety reasons, the electric steering lock is not supplied with current while the vehicle is being driven. The electric steering lock is only supplied with voltage for the unlocking procedure or locking procedure.
Unlocking the electric steering lock
The unlocking procedure starts when terminal R is switched on. After recognition of valid access rights, the CAS triggers the operation for unlocking the electric steering lock. First, the CAS switches the electric steering lock on. The vehicle condition and the status of the electric steering lock are then checked. Finally, the encoded signal is sent to release the lock. Once it has received the valid authorization, the electric steering lock initiates the unlocking procedure. The electric steering lock drive is actuated to "unlock".
| Item | Explanation |
|---|---|
| 1 | Steering column tube |
| 2 | Case Covers |
| 3 | Drive with gearing and lock |
The motor moves a driver via a single-stage gear. The driver pulls the locking bolt into the unlocked position until the locking lever locks into place. The end position of the locking lever is picked up by a Hall sensor. The motor stops when the electric steering lock detects the "unlocked and deadlocked". This status is sent via K-CAN to the CAS. The CAS interrupts the power supply. In the current-free state, the locking lever is locked automatically.
Start enable is granted by the CAS control unit. A start enable is only granted after an error-free plausibility check. The CAS control unit must detect the status "unlocked and secured" without errors. For an engine start, the CAS must have switched off the power supply to the electric steering lock.
For vehicles with Comfort Access, the remote key is also an ID transmitter. A valid ID transmitter must be detected inside the vehicle for the electric steering lock to be unlocked.
To lock the electric steering lock:
When all the conditions for locking have been met, the CAS initiates the locking procedure. The CAS switches the power supply for the electric steering lock on and checks its status. When the status has successfully been validated, the CAS sends the lock enable signal to the electric steering lock. The locking procedure is started. The motor moves a driver via a single-stage gear. The driver pulls the locking bolt in to the lock position until the locking lever engages. The end position of the locking lever is picked up by a Hall sensor. If the electric steering lock detects the position "not unlocked and secured", the engine is stopped. This status is sent via the body bus to the CAS. The CAS interrupts the power supply. When no current is applied, the locking lever is automatically locked. If the electric steering lock has already locked without errors, no locking procedure is executed. The electric steering lock once again sends the current status to the CAS control unit.
The electric steering lock is only activated if the following signals indicate that the vehicle is stationary:- Speed signal on the serial interface.- Signal on the driving condition on the CAN bus.
Both signals must indicate the vehicle is at a standstill. This plausibility check only takes place for the locking procedure.
Locking for Comfort Access
For Comfort Access, the vehicle is locked if the button on the outer door handle is pressed. Here, the electric steering lock also locks. On vehicles with Comfort Access, the electric steering lock locks if the engine has been started and the following conditions are satisfied:
- Terminal 15 OFF
- Locking via the button in the outer door handle
If the engine has not been started, the electric steering lock will lock after terminal R has been switched OFF and a door opened. Or secure on vehicle if terminal R was ON.