Ignition ON, function

Function requirements for ignition ON, general points

 Circuit 30

Ignition ON, general points

For ignition ON, the engine timing 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 circuit 15 relay (F58kR) is switched on based on the electronic ignition lock control unit (N73) operating via the interior CAN (CAN B) and the SAM control unit (N10). The circuit 15 relay conducts the on-board voltage from "circuit 30" to "circuit 15". If a voltage is present at the ME-SFI [ME] control unit at "circuit 15", the engine circuit relay 87M (F58/kN) is actuated by the on-board voltage.

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This causes the relay to close its power contact and the voltage is connected from "circuit 30" (depending on the respective fuses) as "circuit 87 M1.2/2.2" to the ME-SFI [ME] control unit and as "circuit 87 M1.1/1.2/2.2" to the respective engine control sensors and actuators.

The "circuit 31" ground connection is made from the on-board electrical system battery (G1) over the battery ground point (W10) and over a number of ground lines to the firewall ground point (W11).

For ignition ON the CNG control unit (N118/2) supplied by the ME-SFI [ME] control unit by "Circuit 15".

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

- In order to provide full security, the fuel pump (M3) is actuated directly over the fuel system control unit (N118) and also by the FSCU via the drive train CAN (CAN C) (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 chassis CAN (CAN E) for a lamp check.

- Data are exchanged with the electronic ignition lock control unit (circuit 50 signal and drive authorization) over the chassis CAN.

- The throttle valve actuator (M16/6) checks its return spring (by the position of the throttle valve) and may adjust the position of the actuator.

- 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 via the chassis CAN and diagnostic CAN (CAN D) with the ME-SFI [ME] control unit.

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

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

- Ignition maps for adapting the various fuel grades (RON correction (Research Octane Number))

- Mixture maps for enrichment of the fuel-air mixture in different operating states

- Basic setting for idle speed

- Idle speed for engaged gear range

- Temperature correction for switching on and off of the fan motor (M4/7)