Crankcase Ventilation System, Function - GF01.20-P-0001MRD

Engine 274.9 in model 213, 238 

up to model year 2021 

Function requirements, general 

• Engine runs

The ME-SFI [ME] control unit (N3/10) detects engine running via the evaluation of the crankshaft Hall sensor signals (B70). The ME-SFI [ME] control unit directly reads in the signals of the crankshaft Hall sensor.

Crankcase ventilation system, general 

The crankcase ventilation system ensures under all operating conditions of the engine that overpressure and excess gases are dissipated from the crankcase and fed back to the engine via the intake air system for combustion. To balance out the pressure ratio, a separate line is attached for engine ventilation.

The ME-SFI [ME] control unit evaluates the following sensors and signals for the realization of the crankcase ventilation:

• Engine load

  Pressure sensor downstream of throttle valve (B28/7)

• Accelerator pedal position

  The powertrain control unit (N127) directly reads in the accelerator pedal sensor (B37) and transmits this via the drive CAN (CAN C1) to the ME-SFI [ME] control unit.

• Outside temperature

  The front SAM control unit (N10/6) transmits the outside temperature via the interior CAN (CAN B), electronic ignition lock control unit (N73), suspension FlexRay (Flex E), powertrain control unit and drive CAN to the ME-SFI [ME] control unit.

• Bleed line diagnosis (with code 494 (USA version))

  The ME-SFI [ME] control unit directly reads in the bleed line contact switch (S88/5) for the diagnosis of the bleed line between the crankcase and cylinder head.

The function sequence of the crankcase ventilation system is described in the following points:

• Partial-load operation crankcase ventilation 
• Full-load operation crankcase ventilation 

Partial-load operation crankcase ventilation 

In partial-load range, ventilation is performed starting from the oil separator to the charge air distributor. To do so, the partial load operation crankcase ventilation system valve (Y58/2) is arranged in the partial-load vent line.

The valve is actuated in deceleration mode by the ME-SFI [ME] control unit and closes the partial-load vent line from the crankcase to the charge air distributor.

The inflow of exhaust from the crankcase during the mixture adaptation and disruptive background noise are thus avoided. If there is no actuation by the ME-SFI [ME] control unit, the valve is permanently open.

Full-load operation crankcase ventilation 

In wide open throttle operation, ventilation is performed starting from the oil separator to the air intake pipe.

The wide open throttle operation vent line heater element (R39/2) is located in the full load vent line and prevents the freezing of the ventilation system. For this purpose, the heating element is actuated by the ME-SFI [ME] control unit once outside temperatures below 7°C are measured.

Freezing of the crankcase ventilation system and associated engine damage are thus prevented.

View of engine from the left 

Courtesy of MERCEDES-BENZ USA

	Electrical function schematic for crankcase ventilation system		PE01.20-P-2001-97DBD
	Overview of system components for gasoline injection and ignition system with direct injection	Engine 274.9 in model 213.050/053/153 up to model year 2021	GF07.70-P-9998MRP
		Engine 274.9 in model 213 (except 213.050/053/153), 238 up to model year 2021	GF07.70-P-9998MRD