Ignition On, Function - GF07.10-P-1000MMV

Engine 276.8 in model 205, 253 

Function requirements for ignition ON, general points 

• Circuit 30

Ignition ON, general points 

For ignition ON, the engine management in the ME-SFI [ME] control unit (N3/10) is switched on and the engine prepared for starting.

Function sequence for ignition ON 

When the ignition is switched on, the engine compartment circuit 15 relay (K40/8kG) is switched on by the electronic ignition lock control unit (N73) via the interior CAN (CAN B) and the front SAM control unit (N10/6). The "Circuit 15 ON" signal is transmitted redundantly by the electronic ignition lock control unit via the chassis FlexRay (Flex E) to the powertrain control unit (N127) and via the drive train CAN (CAN C1) to the ME-SFI [ME] control unit. The engine compartment circuit 15 relay forwards the on-board electrical system voltage from "circuit 30" to "circuit 15".

If a voltage is applied to the ME-SFI [ME] control unit at "circuit 15", the engine circuit relay 87M (K40/8kN) is actuated by means of a ground signal. This causes the relay to close its power contact and the voltage is forwarded from "circuit 30" (dependent on the respective fuses) as "circuit 87 M4" to the ME-SFI [ME] control unit and as "circuit 87 M1/2/3" to the respective sensors and actuators of the engine management.

If a voltage is present at "circuit 87M", the engine management is switched on and an output stage driver in the ME-SFI [ME] control unit takes over actuation of the engine circuit relay 87M.

The ground connection "circuit 31" takes place from the on-board electrical system battery (G1) over the battery ground point (W10) and over a number of ground lines to the left major assembly compartment electronics ground point (W16/5).

When the engine management is switched on, the ME-SFI [ME] control unit carries out the following functions:

• In order to provide full filling of the fuel low-pressure circuit, the fuel pump (M3) is actuated directly over the fuel system control unit (N118) and also by the FSCU via the drive train CAN (only the first time the ignition is switched ON after the vehicle is unlocked).
• In the instrument cluster (A1) the engine diagnosis indicator lamp (A1e58) is actuated via the drive train CAN, the powertrain control unit, the chassis FlexRay, the electronic ignition lock control unit and the user interface CAN (CAN HMI) for lamp checking purposes.
• An exchange of data with the electronic ignition lock control unit (circuit 50 signal and drive authorization) takes place via the engine CAN (CAN C), the powertrain control unit and the chassis FlexRay (Flex E).
• The throttle valve actuator (M16/6) checks its return spring (by the position of the throttle valve) and adapts the position of the actuator, if necessary.
• The fault memory in the ME-SFI [ME] control unit can be read out and deleted via the diagnostic connector (X11/4). The diagnostic connector is networked to the electronic ignition lock control unit via the diagnostic CAN (CAN D) to the powertrain control unit via the chassis FlexRay and to the ME-SFI [ME] control unit via the drive train CAN.

Correction programming or diagnosis can be carried out with the Xentry diagnostics over the diagnostic connector.

Different characteristics maps for the engine management can be stored and activated with the correction programming in the ME-SFI [ME] control unit, such as:

• Ignition map for adaptation to various fuel grades (RON correction (R  esearch-O  ctane N  umber))
• Mixture maps for enriching the fuel/air mixture in different operating states
• Basic setting for idle speed
• Idle speed for engaged gear range
• Fault setting conditions for smooth running detection
• Temperature correction for switching fan motor (M4/7) on and off