Steering Lock

Steering lock mechanism is designed to prevent ignition key from being removed when parking lock is not engaged. When parking lock is not engaged and brake pedal is not operated, locking pawl rides on outer edge of detent plate. See Fig 1 . Shift and locking valve are held in position in front of blocking cam against force of pressure spring from control cables. Ignition switch CAN NOT be turned to "0" position and key CAN NOT be removed.
To remove ignition key, move selector lever to "P" position and operate brake pedal. Force of tension spring pulls locking pawl under stop of detent plate and pressure spring pushes shift and locking valve off blocking cam enabling blocking cam to turn. See Fig 2 . Ignition switch can now turn to "0" position and key can be removed.

Fig 1: Steering Lock (Parking Lock Not Engaged)
Courtesy of MERCEDES OF NORTH AMERICA

Fig 2: Steering Lock (Parking Lock Engaged)
Courtesy of MERCEDES OF NORTH AMERICA