Drive authorization system level 3 (DAS (FBS) 3), function - GF80.57-P-0003FL

MODEL 212.0/2 up to model year 2014 

Fig 1: Drive Authorization System Function Diagram

Courtesy of MERCEDES-BENZ USA

Positions of transmitter key in electronic ignition lock control unit 

Fig 2: Turning Transmitter Key In Electronic Ignition Lock Control Unit

Courtesy of MERCEDES-BENZ USA

Function requirements, general 

• Circuit 30 ON
• Valid transmitter key

Drive authorization system stage 3 (DAS 3), general 

The DAS 3 allows the ignition to be switched on and the engine to be started. DAS 3 is a compound system consisting of control units, each of which calculate and compare the drive authorization code independently. If the comparison is valid, the immobilizer is released. The following control units are integral parts of the DAS 3 system:

• Electronic ignition switch control unit
• Electric steering lock control unit
• CDI control unit or ME-SFI [ME] control unit
• Fully integrated transmission control unit
• Intelligent servo module for DIRECT SELECT

The DAS [FBS] 3 comprises the following partial functions:

• Function sequence for switching circuit 15C (transmitter key in position "A") 
• Function sequence for switching circuit 15R (transmitter key in position "B") 
• Function sequence for switching circuit 15 (transmitter key in position "C") 
• Function sequence for switching circuit 50 (transmitter key in position "D") 
• Deactivating circuits 

Function sequence for switching circuit 15C (transmitter key in position "A") 

When the transmitter key is inserted into the electronic ignition lock control unit, it switches on the inductive power transmission (power supply to the transmitter key). The transmitter key and the electronic ignition lock control unit exchange encrypted data via infrared for identification of the transmitter key.

The identification code is computed in dialog between transmitter key and the electronic ignition lock control unit using the so-called Hash method. The electronic ignition lock control unit transmits the hash value to the other control units involved. Check, release and feedback is performed separately by each control unit.

The hash method is single-way encryption which prevents the vehicle from being started with an invalid transmitter key. With this method a new number combination is calculated from the old number combination. It is not possible to calculate vice versa. Number combinations already calculated cannot be calculated again.

The electronic ignition lock control unit already calculates the next hash values. After end of calculation, the electronic ignition lock control unit switches off power transmission.

After positive identification of the transmitter key the following operations are accomplished:

• Key position recognition switched on
• Waking up CAN
• Output of circuit 15C
• Unlocking steering lock with electric steering lock control unit

The vehicle can be started when the battery in the transmitter key is discharged. The buttons of the transmitter key are not active as long as it is inserted in the electronic ignition lock control unit. A message is output in the instrument cluster if an invalid transmitter key is used.

Function sequence for switching circuit 15R (transmitter key in position "B") 

Circuit 15Ris actuated by turning transmitter key to position "B". The terminal status 15R is output via all CAN data buses.

The steering lock is locked by the electric steering lock control unit. The transmitter key can no longer be removed in position "B".

Function sequence for switching circuit 15 (transmitter key in position "C") 

Turning the transmitter key to position "C" actuates circuit 15. The circuit 15 status is issued over all the CAN data buses. Power-intensive consumers are supplied by circuit 15X.

Parallel to this, an encrypted DAS 3 request is transmitted to the ME control unit or CDI control unit, the fully integrated transmission control unit and the intelligent servo module for DIRECT SELECT.

Function sequence for switching circuit 50 (transmitter key in position "D") 

The starter (M1) is actuated via the ME control unit or CDI control unit by turning the transmitter key to position "D". The terminal status for circuit 50 is output via all CAN data buses. Terminal 15X is removed from the corresponding CAN until terminal 50 is OFF and the engine is running (time control, if applicable).

When circuit 15X is switched off, the electrical consumers are switched off to facilitate starting the engine. The transmitter key automatically returns to position "C" when released.

Deactivating circuits 

Turning transmitter key back to left switches off the engine. The following functions are implemented in the electronic ignition lock control unit:

• Transmitter key in position "B"
  • Circuit 15 and circuit 15X OFF
• Transmitter key in position "A"
  • Circuit 15R OFF
  • The transmitter key can be removed, the steering lock is locked by the electric steering lock control unit

    MODEL 212.0/2 with TRANSMISSION 722.6

up to model year 2014

The transmitter key can be removed, when the selector lever position "P" is engaged.

The electronic ignition lock control unit can request a new check for identification of the transmitter key during restart without previously removing the transmitter key.

MODEL 212.0/2 with TRANSMISSION 722.9, 724

up to model year 2014

The transmission changes automatically to the park position, when the driver door is opened or the transmitter key is removed when the vehicle is standing still.

MODEL 212.0/2 with TRANSMISSION 722.9

up to model year 2014

If the communication between the electronic ignition lock control unit and intelligent servo module for DIRECT SELECT is erroneous or missing, actuation is performed via the emergency path. The on-board electrical system power is switched to the emergency path and the park position is engaged.

After eliminating the fault, the electrical and mechanical components for this function are synchronized.