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ME-SFI lambda control, function - GF07.61-P-4022V

ENGINES 272.920 in MODEL 203 up to model year 2008 /AEJ 07 

ENGINES 272.922 in MODEL 211 

ENGINES 272.940 in MODEL 203 up to model year 2008 /AEJ 07 

ENGINES 272.941 in MODEL 203 up to model year 2008 /AEJ 07 

ENGINES 272.942 in MODEL 171 up to model year 2008 /AEJ 07 

ENGINES 272.943 in MODEL 211, 219 

ENGINES 272.944 in MODEL 211 

ENGINES 272.945 in MODEL 251 up to model year 2008 /AEJ 07 

ENGINES 272.946 in MODEL 221 up to model year 2008 /AEJ 07 

ENGINES 272.960 in MODEL 203 up to model year 2008 /AEJ 07 

ENGINES 272.963 in MODEL 171 up to model year 2008 /AEJ 07 

ENGINES 272.964 in MODEL 211, 219 

ENGINES 272.965 in MODEL 221 up to model year 2008 /AEJ 07 

ENGINES 272.966 in MODEL 230 up to model year 2008 /AEJ 07 

ENGINES 272.967 in MODEL 164, 251 up to model year 2008 /AEJ 07 

ENGINES 272.970 in MODEL 203 up to model year 2008 /AEJ 07 

ENGINES 272.972 in MODEL 211 

ENGINES 272.975 in MODEL 221 up to model year 2008 /AEJ 07 

ENGINES 273.922 in MODEL 221 up to model year 2008 /AEJ 07 

ENGINES 273.923 in MODEL 164 up to model year 2008 /AEJ 07 

ENGINES 273.924 in MODEL 221 up to model year 2008 /AEJ 07 

ENGINES 273.960 in MODEL 211, 219 

ENGINES 273.961 in MODEL 216, 221 up to model year 2008 /AEJ 07 

ENGINES 273.962 in MODEL 211 

ENGINES 273.963 in MODEL 164, 251 up to model year 2008 /AEJ 07 

ENGINES 273.965 in MODEL 230 up to model year 2008 /AEJ 07 

ENGINES 273.967 in MODEL 209 

ENGINES 273.968 in MODEL 221 up to model year 2008 /AEJ 07 

ENGINES 272.940 in MODEL 209 

ENGINES 272.960 in MODEL 209 

Shown on engine 272 

Fig 1: ME-SFI Lambda Control Function Diagram
G07587118Courtesy of MERCEDES-BENZ USA

The mixture composition is maintained within limits as close as possible to λ=1 in order to achieve a high conversion of the exhaust gases in the catalytic converter.

The O 2 sensors detect the oxygen share in the exhaust and transmit corresponding signals to the ME-SFI [ME] control unit. This changes the mixture composition so that in all engine operating statuses, the desired oxygen (usually λ=1) is set. This procedure is repeated (control loop), the control speed is dependent on engine load and speed.

The lambda closed-loop control is operational in the following operating conditions (closed-loop control):

Fig 2: Three Way Catalytic Converter Exhaust Gas Conversion Graph
G07587119Courtesy of MERCEDES-BENZ USA
Fig 3: Lambda Control Loop Diagram
G07587120Courtesy of MERCEDES-BENZ USA

Lambda control loop 

Assuming a leaner air/fuel mixture is produced. The consequence of this is that the O2 sensor voltage drops and the ME-SFI [ME] control unit compensates for this lean drift by enriching the mixture accordingly. This makes it possible to achieve an air/fuel composition of approximately λ=1. The reading of the lambda control factor with the STAR DIAGNOSIS moves towards +25% The more the lambda control factor moves towards +25%, the leaner is the air/fuel mixture and the greater is the enrichment of the mixture on the part of the ME-SFI [ME] control unit.

Fig 4: Lambda Control Factor Chart (Star Diagnosis)
G07587121Courtesy of MERCEDES-BENZ USA
  Component description for ME-SFI [ME] control unit   GF07.61-P-6000V 
  Component description for O 2 sensors O2 sensors upstream of catalytic converter GF07.04-P-6100V
O2 sensors downstream of catalytic converter GF07.04-P-6100VA
  Component description for crankshaft Hall sensor   GF07.04-P-6220V
  O2 sensor heater, function   GF07.61-P-3025V
  Component description for hot film mass air flow sensor   GF07.07-P-6000V
  Component description for coolant temperature sensor   GF07.04-P-6040V
  Self-adjustment of mixture formation, function   GF07.10-P-1029V
  Component description for accelerator pedal sensor   GF30.20-P-2010V
  Component description for three-way catalytic converter   GF07.03-P-6010V
  ME-SFI two-sensor control, function   GF07.61-P-3020V
  Component description for three-way catalytic converter   GF49.10-P-2010V