Electronic ignition/starter switch control module, purpose - GF80.57-P-4102-03R

The EIS control module (N73)  has the following purpose:

• Checking and controlling access authorization 
• Checking and controlling drive authorization 
• Infrared communication with remote control key (A8/1)  when inserted and inductive energy transmission to remote control key (A8/1) 
• Transmission of check value for key for enabling of electronic selector lever module (EWM) (if present) and engine control module
• Rotation angle-dependent activation of individual circuits (15, 15R)
• Prefastening and holding key in unturned position
• Locking key in turned position
• Key rotation lock by locking solenoid
• Positioning key in key channel
• Return position between start and driving position
• Locking key opening when key is removed
• Assignment of key to memory functions
• Actuation of electric steering lock  (only in combination with convenience manual transmission)

Gateway function 

The EIS control module (N73)  serves as interface (gateway) between passenger compartment CAN bus and engine compartment CAN bus  for exchanging data between the two bus systems.

Diagnosis functions 

• The EIS control module (N73)  connects between the control modules of the passenger compartment CAN bus and the data link connector (X11/4)  .

Shift lock function 

The mechanical shift lock function prevents the key from being turned back to position "0" when the selector lever is not  in the "P" position.

Coding equipment versions 

The equipment versions  are coded in the EIS control module (N73). 

Provision of circuits: 

• C. 15C  to passenger compartment CAN bus
• C. 15R  to passenger compartment CAN bus and as hardware output
• C. 15  to passenger compartment CAN bus, engine compartment CAN bus and as hardware output
• C. 15X  to passenger compartment CAN bus (c. 15X serves for switching off loads, e.g. fan motor, during starting operation.

  C. 15X is ON, when the engine is running stably or  when c. 15 is ON and an attempt is not being made or has not been made to start the engine.

• C. 50  to passenger compartment CAN bus and engine compartment CAN bus

Scanning the following switches: 

• Combination switch (S4); voltage coded
• VCS switch (S93/2); voltage coded
• CC switch
• Left multifunction steering wheel pushbutton group (S110)
• Right multifunction steering wheel pushbutton group (S111)

Reading in button for multifunction steering wheel 

The buttons of the multifunction steering wheel are read in voltage-coded by the EIS control module (N73)  via the horn/airbag contact spiral (A45). 

Observe the following peculiarities:

• All buttons on the multifunction steering wheel are read in directly by the EIS control module (N73)  over two  leads only.

  Voltage coding of the various button functions using only various resistances corresponding to the incrementation would not ensure sufficient insensitivity to interference. For this reason, the buttons are read in as follows:

• The voltage generated by the EIS control module (N73)  for checking the buttons permanently changes its polarity. 

The buttons for the multifunction steering wheel are subdivided into two groups (left and right button group (S110, S111) with associated buttons for fanfares).

• A diode with different polarity for the two groups is connected in series with each of these pushbutton groups.
• Depending on the polarity of the test voltage of the EIS control module (N73)  the right or left group of pushbuttons is checked alternately. The button check "switches" back and forth between the two switch groups  . The actual voltage coding is therefore accomplished within one group of buttons only.

Priorities 

If more than one button is pressed simultaneously within one button group  of the multifunction steering wheel always only one function is activated by the EIS control module (N73)  . This requires different priorities  for the various functions within  one button group. The button with the lowest resistance value (fanfare button) has the highest priority