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

Engine 264.9 in Model 205, 253 

Function requirements, general 

• Gear range "P" or "N" engaged
• Foot brake actuated

The fully integrated transmission control unit (Y3/8n4) transmits information about the engaged gear range via the drive train CAN (CAN C1) to the ME-SFI [ME] control unit (N3/10).

The Electronic Stability Program control unit (N30/4) transmits information about the status of the service brake via the chassis FlexRay (Flex E), the powertrain control unit (N127) and the drive train CAN to the ME-SFI [ME] control unit.

Start 

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

• Intake camshaft position for ignition circuit detection

  Intake camshaft Hall sensor (B6/15)

• Exhaust camshaft position for ignition circuit detection

  Exhaust camshaft Hall sensor (B6/16)

• Coolant temperature

  Coolant temperature sensor (B11/4)

• Engine speed

  Crankshaft Hall sensor (B70)

• Circuit 50 status

  The electronic ignition lock control unit (N73) reads in the signals of the KEYLESS-GO start/stop button (S2/3) directly, and transmits the status of circuit 50 via the suspension FlexRay, the powertrain control unit, and the drive CAN to the ME-SFI [ME] control unit.

• Oil level

  Engine oil fill level sensor (B40/6)

• Drive range, transmission oil temperature

  The fully integrated transmission control unit transmits information via the drive CAN to the ME-SFI [ME] control unit.

• Condition and voltage of the 48 V on-board electrical system, charge level of the 48 V on-board electrical system battery (G1/3) (with code B01 (48V Technology))

  The DC/DC converter control unit (N83/1) transmits the information via the interior CAN (CAN B), the electronic ignition lock control unit, the suspension FlexRay, the powertrain control unit, and the drive CAN to the ME-SFI [ME] control unit.

• Status of starter-alternator (M1/10) (with code B01 (48V Technology))

  The powertrain control unit reads in the signals of the starter-alternator via the hybrid CAN (CAN L) and sends the status (alternator rotational speed and torque) via the drive CAN to the ME-SFI [ME] control unit.

The ME-SFI [ME] control unit actuates the following assembly parts to start the Engine:

• Starter (M1) via circuit 50 starter relay (K40/8kH) (except code B01 (48V Technology))
• Cylinder 1 ignition coil (T1/1)
• Cylinder 2 ignition coil (T1/2)
• Cylinder 3 ignition coil (T1/3)
• Cylinder 4 ignition coil (T1/4)
• Cylinder 1 fuel injector (Y76/1)
• Cylinder 2 fuel injector (Y76/2)
• Cylinder 3 fuel injector (Y76/3)
• Cylinder 4 fuel injector (Y76/4)
• Fuel pump (M3)

  The ME-SFI [ME] control unit transmits the request to actuate the fuel pump directly and via the drive CAN to the fuel system control unit (N118). The ME-SFI [ME] control unit additionally transmits the specified fuel pressure via the drive CAN to the fuel system control unit. The fuel system control unit directly actuates the fuel pump.

• Starter-alternator (with code B01 (48V Technology))

  The ME-SFI [ME] control unit transmits the request to start the Engine via the Engine CAN (CAN C) to the powertrain control unit.

  The powertrain control unit evaluates all relevant variables and sends the request to start the Engine via the hybrid CAN to the starter-alternator.

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 intake camshaft and exhaust camshaft Hall sensors.

Start begin 

By actuating the KEYLESS-GO start/stop button, the ME-SFI [ME] control unit receives the "circuit 50 signal" from the electronic ignition lock control unit via the suspension FlexRay, powertrain control unit and drive CAN.

Vehicles except code B01 (48V Technology) 

The ME-SFI [ME] control unit actuates the circuit 50 starter relay on both sides with a ground signal. The power contact of the starter circuit 50 relay closes and the solenoid switch of the starter is supplied at "circuit 50" with a voltage from "circuit 30".

Vehicles with code B01 (48V Technology) 

The ME-SFI [ME] control unit transmits the request to start the Engine via the Engine CAN to the powertrain control unit. The powertrain control unit evaluates all relevant variables and transmits the request to start the Engine via the hybrid CAN to the starter-alternator.

When the KEYLESS-GO start/stop button is operated, the ME-SFI [ME] control unit requests the starting procedure from the powertrain control unit.

When the starting procedure is initiated, the shutting off of "circuit 50" will have no further influence on the starting procedure. The start process can only be canceled if circuit 15 is switched off.

Engine 264.9 in Model 205, 253

except code B01 (48V Technology)

At the positive pole of the on-board electrical system battery (G1), the voltage dip limiter (R62) is installed. It is connected to the circuit 50 relay for starter via circuit 50. On starting the Engine, the voltage dip limiter engages the integrated series resistor. This reduces the starter's power consumption when the Engine is cranked. The voltage drop that is perceptible to the vehicle occupants when starting the Engine is reduced. If the on-board electrical system voltage drops too much due to the high power consumption of the starter, the voltage dip limiter switches the series resistor off again.

Ending start 

Starter control is carried out automatically by the ME-SFI [ME] control unit (touch start). This means that once a starting procedure is initiated, deactivating "circuit 50" no longer has an influence on the starting procedure.

Vehicles except code B01 (48V Technology) 

When Engine cranking speed has reached 400 to 700 RPM, or after a starting time of 5 to 40 s (dependent on coolant temperature), the ME-SFI [ME] control unit interrupts the negative activation of the circuit 50 starter relay and thus terminates the starting procedure.

Vehicles with code B01 (48V Technology) 

The ME-SFI [ME] control unit transmits the Engine speed via the Engine CAN to the powertrain control unit. On reaching the Engine cranking speed of 400 to 700 RPM or a starting time of approx. 5 to 40 s (depending on the coolant temperature), the powertrain control unit stops the starting procedure and transmits the "Engine running" signal to the DC/DC converter control unit via the suspension FlexRay, electronic ignition lock control unit and interior CAN.

The start process can be broken off through renewed actuation of the KEYLESS-GO start-stop button.

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