GF80.57-P-0003RI Drive Authorization System Level 3 (DAS (FBS) 3), Function

GF80.57-P-0003RI Drive Authorization System Level 3 (DAS [FBS] 3), Function

Component Identification:

Function requirements, general
^ Circuit 30 ON
^ Valid transmitter key
^ Transmitter key inserted

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:
- EZS control unit
- ME-SFI [ME] control unit (N3/10)
- Electronic selector lever module control unit (N15/5)
- Fully integrated transmission control unit (VGS) (Y3/8n4) 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 EZS 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 EZS control unit for identification.

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

Hash method:
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 EZS control unit. After completion of the calculation, the energy transmission is switched off. After positive identification the following is performed:
- Key position recognition switched on
- Wake-up of engine compartment CAN and interior CAN
- Output of circuit 15C

The vehicle can still 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 EZS 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 15 (transmitter key in position "B")
Circuit 15R is actuated by turning transmitter key to position "B". The status of circuit 15R is output to engine compartment CAN and interior CAN.

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 status of circuit 15 is output to engine compartment CAN and interior CAN. Power-intensive consumers are supplied by circuit 15X.
Parallel to this, an encrypted DAS 3 query is transmitted to the ME control unit, electronic selector lever module control unit and fully integrated transmission control unit (VGS).

Function sequence for switching circuit 50 (transmitter key in position "D")
The starter (M1) is actuated via the ME control unit by turning the transmitter key to position "D". The status for circuit 50 is output to the interior CAN or engine compartment CAN.
Circuit 15X is removed from the interior CAN and the engine compartment 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

Deactivating circuits
Turning transmitter key back to left switches off the engine. The following functions are implemented in the EZS control unit:

Transmitter key in position "B"
- Switch off signals circuit 15 and circuit 15X
- Circuit 15R is switched on

Transmitter key in position "A"
- Circuit 15R Off
- Transmitter key can be removed (the transmitter key can only be removed when the selector lever in the "P" position)

The EZS control unit can request a new check for identification of the transmitter key during restart without removing the key.