Ignition, Function - GF07.10-P-1023MNH
Engine 176.9, 177.9 in model 463
as of model year 2019
Ignition, general points
The partial function ignition describes the behavior of the engine management in ME-SFI [ME] control unit (N3/10) for first switching on of the ignition, for which the engine is prepared for starting, and for switching off of the ignition, for which first the engine and then the engine management is switched off.
The function sequence is described in the following steps:
- Function sequence for ignition ON
- Function sequence for ignition OFF
Function requirements for ignition ON, general points
- Terminal 30
Function sequence for ignition ON
Upon switching on the ignition the engine compartment terminal 15 relay (K40/8kG) is switched on by the electronic ignition lock control unit (N73) via the interior CAN (CAN B).
The "Circuit 15 ON" signal is transmitted redundantly to the ME-SFI [ME] control unit via the suspension FlexRay (Flex E), powertrain control unit (N127), and Drivetrain CAN (CAN C1). 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. The relay thus closes its power contact and the voltage is forwarded from "Circuit 30", depending on the relevant fuses, as "Circuit 87 M4" to the ME-SFI [ME] control unit and as "Circuit 87 M1/2/3" to the relevant 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 "circuit 31" ground connection is made from the on-board electrical system battery (G1) via the battery sensor ground point (W10) and via several ground lines to the right front wheel arch ground point (W3/1).
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 via the Drivetrain CAN (only the first time the ignition is switched ON after the vehicle is unlocked).
- In the instrument cluster (A1) the engine diagnosis symbol is actuated for a symbol check over the Drivetrain CAN, powertrain control unit, suspension FlexRay, electronic ignition lock control unit and the user interface CAN (CAN HMI).
- The left and right left throttle valve actuators (M16/60, M16/61) check their return springs (via actuation of the left and right throttle valve actuator motors (M16/60m1, M16/61m1)) and carry out - if necessary - an actuator adaptation via the position determination of the throttle valve by means of the actual value potentiometers 1 and 2 on the left and right (M16/60r1, M16/60r2, M16/61r1, M16/61r2).
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 diagnostic CAN (CAN D), electronic ignition lock control unit, chassis FlexRay, powertrain control unit and Drivetrain CAN with the ME-SFI [ME] control unit.
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
Function requirements for ignition OFF, general points
- Circuit 87M (Engine management ON)
- Circuit 15 (ignition ON)
Function sequence for ignition OFF
For ignition OFF the circuit 15 engine compartment relay is switched off by the electronic ignition lock control unit via interior CAN and front SAM control unit (N10/6). The "Circuit 15 OFF" signal is transmitted redundantly via the suspension FlexRay, powertrain control unit and drive CAN to the ME-SFI [ME] control unit.
If the ME-SFI [ME] control unit receives the "Circuit 15 OFF" signal via the engine compartment circuit 15 relay, the engine is switched off by deactivating the fuel pump, the fuel injectors for cylinders 1 up to 8 (Y76/1 up to Y76/8) and the ignition coils for cylinders 1 + 2 up to cylinders 7 + 8 (T4 up to T4/3) and the computer run-on is started.
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MNH |