Starting, Function - GF07.10-P-1001MNH

Engine 176.9, 177.9 in model 463 

as of model year 2019 

Function requirements for starting, function 

• Circuit 87M ON (Engine management ON)
• Drive authorization system 4 (DAS 4) start enable
• Engaged gear range "P" or "N"

The circuit relay 87M (K40/8 kN) is switched on for circuit 15.

The fully integrated transmission control unit (Y3/8n4) transmits the status of the drive range via drive CAN (CAN C1) to the ME-SFI control unit (N3/10).

Starting, general points 

The ME-SFI control unit reads in the following signals for starting:

• Left intake camshaft Hall sensor (B6/4) and right intake camshaft Hall sensor (B6/5), intake camshaft positions for ignition circuit detection
• Left exhaust camshaft Hall sensor (B6/6) and right exhaust camshaft Hall sensor (B6/7), exhaust camshaft positions for ignition circuit detection
• Coolant temperature sensor (B11/4)
• Crankshaft Hall sensor (B70), engine rpm
• Circuit 50 signal

  Electronic ignition lock control unit (N73), "Circuit 50 signal" via suspension FlexRay (Flex E), powertrain control unit (N127) and drive CAN

The ME-SFI control unit actuates the following assembly parts to start the engine:

• Starter (M1) via the circuit 50 starter relay (F58kM)

  The ME-SFI control unit actuates the circuit 50 starter relay directly.

• Remove ignition coils (cylinder 1 + 2 ignition coil to cylinder 7 + 8 ignition coil (T4 to T4/3))
• Fuel injectors (fuel injector for cylinders 1 to 8 (Y76/1 to Y76/8))
• Fuel pump (M3) over the FSCU (N118)

The ME-SFI control unit coordinates the injection and firing order during starting based on the signals from the crankshaft Hall sensor and the camshaft Hall sensors.

The starter control in the ME-SFI control unit takes on actuation and cutout of the starter.

Function sequence for start 

The starter control is subdivided into the following points:

• Function sequence for start begin 
• Function sequence for start end 

Function sequence for start begin 

Through actuation of the KEYLESS-GO start-stop button (S2/3), the ME-SFI control unit receives the "circuit 50 signal" from the electronic ignition lock control unit via the drive CAN, the powertrain control unit, and the suspension FlexRay.

The ME-SFI control unit uses a ground signal to actuate the starter circuit 50 relay (K40/8kH) on both sides. The power contact on the starter relay closes and the starter solenoid switch is supplied at "circuit 50" with voltage from "circuit 30".

Function sequence for start end 

Starter control is carried out automatically by the ME-SFI control unit (touch start). This means that once the start process is initiated, switching off "circuit 50" will have no further influence on the start procedure.

When the engine cranking speed has reached approx. 400 to 700 rpm or a start time of approx. 5 to 40 s (depending on the coolant temperature), the ME-SFI control unit interrupts negative activation to the circuit 50 starter relay thereby ending the start procedure.

When actuating the ignition key the starting procedure can only be aborted by switching off the ignition.

During the starting procedure with the KEYLESS-GO start/stop button, the engine start can be aborted by tapping the button again.

A voltage dip limiter (G1) is installed at the positive pole of the on-board electrical system battery.

Its task is to prevent a drop in the battery voltage below a defined voltage value during the starting procedure of the engine.

This is performed through temporary limitation of the starter current. Note here that a voltage of 12 V is present at the starter positive line only during the starting procedure.

	Electrical function schematic for starting		PE07.10-P-2701-97ZGF
	Overview of system components for gasoline injection and ignition system with direct injection		GF07.70-P-9998MNH