Drive authorization system level 3 (DAS [FBS] 3), function (MODEL 204.0/2 as of model year 2009/YoM 08, 204.3, 204.9) - GF80.57-P-0003CE

MODEL 204.0/2 as of model year 2009/YoM 08

MODEL 204.3

MODEL 204.9

Fig 1: Drive Authorization System, Stage 3 (DAS 3) Function Diagram

Courtesy of MERCEDES-BENZ USA

Positions of transmitter key in electronic ignition lock control unit

Fig 2: Identifying Positions Of Transmitter Key In Electronic Ignition Lock Control Unit

Courtesy of MERCEDES-BENZ USA

Function requirements, general

Circuit 30 ON
Valid transmitter key inserted into electronic ignition lock control unit

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 check in question is valid, each component is released automatically.

The following control units are integral parts of the DAS 3 system:

Electronic ignition lock control unit

Electric steering lock control unit
CDI control unit (with diesel engine) or
ME-SFI [ME] control unit (with gasoline engine)
Fully integrated transmission-control control unit (with transmission 722.9)

The DAS 3 system comprises the following subfunctions:

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 for power supply to the transmitter key. Encrypted data is exchanged via infrared signals between the transmitter key and the electronic ignition lock control unit 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 next Hash values are computed in the electronic ignition lock control unit. After completion of the calculation, the energy transmission is switched off.

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

Key position recognition switched on
Wake up of controller area network (data bus/CAN Bus) (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 dead.

The function keys of the transmitter key are not active as long as the electronic ignition lock control unit is inserted A message is output in the instrument cluster (A1) if an invalid transmitter key is used.

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

Circuit 15R is actuated by turning transmitter key to position "B". The circuit status 15R is output over 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")

Circuit 15 is actuated by turning transmitter key to position "C". The circuit 15 status is output over all CAN data buses. Power-intensive consumers are supplied by circuit 15X.

Parallel to this, an encrypted DAS 3 query is sent to the ME control unit or CDI control unit and the fully integrated transmission control unit.

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 circuit 50 status is output over all CAN data buses.

Circuit 15X is removed from the corresponding CAN as long as the circuit 50 is off again 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"

Switch off signals from circuit 15 and circuit 15X

Transmitter key in position "A"

Terminal 15R OFF
Transmitter key can be removed, steering lock locked with electric steering lock control unit (on vehicles with transmission 722 the transmitter key can only be removed when the selector lever is in position "P")

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.

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