Drive authorization system level 3 (DAS [FBS] 3), function (Model 204.0/2 up to model year 08/YoM 07) - GF80.57-P-0003CW

Model 204.0/2 up to model year 08/YoM 07

Fig 1: Identifying Positions Of Transmitter Key

Courtesy of MERCEDES-BENZ USA

Description

The drive authorization system stage 3 (FBS 3) is a combination of control units consisting of:

Electronic ignition lock control unit (N73)

Electric steering lock control unit (N26/5)
ME-SFI control unit (N3/10) (with gasoline engine) or CDI control unit (N3/9) (with diesel engine)
Electronic transmission control unit (N15/3) (on transmission 722.6) or Fully integrated transmission control unit (Y3/8n4) on transmission 722.9)

The encrypted data is exchanged between the transmitter key and the electronic ignition lock control unit via infrared signal The code is computed in dialog between the transmitter key and the electronic ignition lock control unit using the Hash method.

The corresponding Hash value of the transmitter key is transmitted to the other control units by the electronic ignition lock control unit.

Check, release and feedback is performed separately by each control unit.

Hash function

The encrypted base module of the DAS 3 is a so-called Hash function. The most important property of the Hash function is the one-way characteristic. This means that another number can be calculated using the Hash function from an initial number, however that calculation of the initial number in the opposite order is practically impossible.

Function sequence

When the transmitter key is inserted in the electronic ignition lock control unit it is inductively supplied with power, so that even when the transmitter key's battery is dead the vehicle can still be started. Communication between the transmitter key and the electronic ignition lock control unit is made via infrared signal.

The function keys of the transmitter key are not active as long as the electronic ignition lock control unit is inserted

Transmitter key in position "A"

The inductive energy transmission to the voltage supply of the transmitter key is switched on.
Encrypted data exchange between transmitter key and electronic ignition lock control unit for identification.

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 the following is performed:

Release of lift solenoid for rotary lock in release electronic ignition lock control unit for transmitter key.
Switch-on of key position recognition.
Wake-up of chassis CAN and interior CAN
Output of circuit 15C.
Encrypted data exchange between electronic ignition lock control unit and electric steering lock control unit for identification. Following successful communication, the steering lock is unlocked by the electric steering lock control unit and secured.

A message is output in the instrument cluster (A1) if an invalid transmitter key is used.

Transmitter key in position "B"

Actuation of circuit 15R.
Output of status circuit 15R to chassis CAN and interior CAN

The transmitter key can no longer be removed in position "B".

Transmitter key in position "C"

Circuit 15 is actuated.
Output of status circuit 15 to chassis CAN, interior CAN, and circuit 15X (supply of intensive current consumers).
Encrypted request to ME-SFI control unit or CDI control unit
Encrypted request for transmission control unit

Transmitter key in position "D"

Actuation of starter (M1) via ME-SFI control unit or CDI control unit.
Output of status circuit 50 to interior CAN and chassis CAN
Circuit 15X is removed from the interior CAN and the chassis CAN until circuit 50 is off again and the engine is running (circuit 61) (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

Switch off engine

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 circuit 15 and circuit 15X.
Circuit 15R remains switched on.
Set chassis CAN and interior CAN communication.

Transmitter key in position "A"

The steering lock is locked by the electric steering lock control unit.
Open load switch circuit 15R.

The transmitter key can be removed (on vehicles with transmission 722 the transmitter key can only be removed after the electronic selector lever module control unit (N15/5) has been shifted to "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.

Electrical function schematic for drive authorization system (DAS)		PE80.57-P-2050-99FAA
Drive authorization system, stage 3 (DAS 3), location of components		GF80.57-P-0003-01CW
Drive authorization system, stage 3 (DAS 3), block diagram		GF80.57-P-0003-02CW
Transmitter key, component description	A8/1	GF80.57-P-6010CW
Electric steering lock control unit component description	N26/5	GF80.57-P-6021CW
Component description for electronic ignition lock control unit	N73	GF80.57-P-6001CW