Starting System: Description and Operation

GF07.10-P-1001MI Starting, Function

Starting function requirements, general points
^ Circuit 87M ON (engine control ON)
^ Engine OFF
^ Drive authorization system 3 (DAS 3) start enable
^ Engaged gear range "P" or "N"

Starting, general points
For the starting, the ME-SFI [ME] control unit (N3/10) reads the following sensors and signals:
- LH and RH intake camshaft Hall sensors (B6/4, B6/5), intake camshaft positions for ignition circuit detection
- LH and RH exhaust camshaft Hall sensors (B6/6, B6/7), exhaust camshaft positions for ignition circuit detection
- Coolant temperature sensor (B11/4)
- Crankshaft Hall sensor (B70), engine speed
- Start enable clutch pedal switch (S40/5) (for manual transmission and code (494) USA version)
- Electronic ignition lock control unit (N73), "circuit 50 signal" via the chassis CAN (CAN E)

The ME-SFI [ME] control unit actuates the following components to start the engine:
- Starter (M1)
- Ignition coils (T1)
- Injection valves (Y62)
- The fuel system control unit (N118) directly and via the drive train CAN (CAN C) and thus the fuel pump (M3)

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

Start function sequence
The starter control is sub-divided into the following points:
^ Function sequence for start begin
^ Start end function sequence (for automatic transmission)
^ Start end function sequence (for manual transmission)

Function sequence for start begin
When the transmitter key (transmitter key (A8/1)) is moved to the start position, the ME-SFI [ME] control unit receives the "circuit 50 signal" from the electronic ignition lock control unit via the chassis CAN.
The ME-SFI [ME] control unit actuates the circuit 50 starter relay (N10/1kM) with a ground signal. The power contact on the starter relay closes and the starter solenoid switch is supplied at "circuit 50" with voltage from "circuit 30"

Start end function sequence (for automatic transmission)
Start control is carried out automatically by the ME-SFI [ME] control unit (touch start). This means that if the start process is initiated switching off of "circuit 50" has no further influence on the start process.

When engine cranking speed has reached 400 to 700 rpm, or after a starting time of 5 to 40 s (depending on coolant temperature), the ME-SFI control unit interrupts the negative activation of the circuit 50 starter relay and thus terminates the start sequence.
The start sequence can only be aborted by switching off the ignition.

Start end function sequence (for manual transmission)
On reaching an engine cranking speed of 400 to 700 rpm or upon disappearance of the "circuit 50 signal" the ME-SFI [ME] control unit interrupts the negative activation to the circuit 50 starter relay and thus ends the starting procedure.
The starting procedure can also be aborted by switching off the ignition.