Electronic ignition switch control unit, purpose - GF80.57-P-4102-03Q

Purpose: 

The EIS control module (N73) is incorporated into the vehicle network and forms the gateway between the Control Area Network Bus, class B (passenger compartment) (CAN-B) and the Control Area Network Bus, class C (engine compartment) (CAN-C). It handles all bi-directional data traffic to the transmitter key (A8/1).

The EIS control module (N73) decrypts and encrypts data and performs an authentication test

Function survey: 

• Gateway between CAN-B and CAN-C,
• Coded bi-directional infrared communication to transmitter key (A8/1),
• Energy transmission to transmitter key (A8/1),
• Closing key opening with transmitter key (A8/1) removed
• Transmission of authentication values for releasing electric steering lock control unit (N26/5) and ME-SFI control module (N3/10) (on engine 112, 113 or 271) or CDI control module (N3/9) (on engine 612) with DAS 3 drive authorization system,
• Bus status signal for circuits 15, 15R, 50, 15X, and 15C,
• Rotation angle-dependent activation of individual signals
• Prefastening and holding transmitter key (A8/1) in position 0,
• Locking transmitter key (A8/1) in turned position
• Rotation lock for transmitter key (A8/1) by disabling solenoids
• Shift-lock function in combination with electronic selector lever module control unit (N15/5) (on transmission 722),
• Automatic return from start to driving position

Access authorization via radio and infrared: 

• Communication between rear SAM control module with fuse and relay module (N10/2) and EIS control module (N73).
• Communication between left door control module (N69/1) and EIS control module (N73).

Starting vehicle operating 

Insert transmitter key (A8/1) into EIS control module (N73) (position 0):

The inductive energy transmission to the power supply for the transmitter key (A8/1) is switched on, data (coded) is exchanged between the transmitter key (A8/1) and the EIS control module (N73) for key identification.

After successful communication: 

• Release of locking solenoid for steering column
• Switching on transmitter key position recognition
• Wake-up of CAN-B.
• Rotation release for transmitter key (A8/1).

Key position 1 (transmitter key (A8/1) turned approx. 90° to "Radio position"). 

• Actuating c. 15R.
• Status output of c. 15R to CAN-B.

Key position 2 (transmitter key (A8/1) turned another 30° to "Ignition") 

• C. 15 is actuated.
• Status output of c. 15 to CAN-B and CAN-C as well as c. 15X to CAN-B.
• Coded enabling of engine management
• Message transfer from CAN-C to CAN-B.
• Message transfer from CAN-B to CAN-C.

Key position 3 (transmitter key (A8/1) turned another 30° to "Engine start") 

• Actuation of starter relay via ME-SFI control module (N3/10) (on engine 112, 113 or 271) or CDI control module (N3/9) (on engine 612).
• Status transfer c. 50 to CAN-B and CAN-C.
• Transmission from c. 15X to CAN-B is interrupted during c. 50 "ON"

Take vehicle out of operation 

• Returning transmitter key (A8/1) to left to key position 1 stops the engine, c. 15R remains switched on.
• On vehicles with electronic selector lever module control unit (N15/5) (on transmission 722) the mechanical shift-lock function prevents the transmitter key (A8/1) from being turned back to key position 0, while the selector lever is shifted to "P". This is performed by a mechanical function in the electronic ignition switch control unit (N73).
• Turning back approx. 90° in key position 0, transmitter key (A8/1) can be removed