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Home >> Mercedes Benz >> 2007 >> ML63 >> Repair and Diagnosis (Single Page) >> Engine Performance >> Ignition System >> Fuel, Ignition, Engine Control - Basic Knowledge - 2 Of 2 -- 164 Chassis >> Basic Knowledge >> ME-SFI lambda control, function - GF07.61-P-4022 >> ME-SFI lambda control, function - GF07.61-P-4022V
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ME-SFI lambda control, function - GF07.61-P-4022V

ENGINE 272.920 in MODEL 203 

ENGINE 272.922 in MODEL 211 

ENGINE 272.940 in MODEL 203, 209 

ENGINE 272.941 in MODEL 203 

ENGINE 272.942 in MODEL 171 

ENGINE 272.943 in MODEL 211 

ENGINE 272.944 in MODEL 211 

ENGINE 272.945 in MODEL 251 

ENGINE 272.946 in MODEL 221 

ENGINE 272.960 in MODEL 203, 209 

ENGINE 272.963 in MODEL 171 

ENGINE 272.964 in MODEL 211, 219 

ENGINE 272.965 in MODEL 221 

ENGINE 272.966 in MODEL 230 

ENGINE 272.967 in MODEL 164, 251 

ENGINE 272.970 in MODEL 203 

ENGINE 272.972 in MODEL 211 

ENGINE 272.975 in MODEL 221 

ENGINE 273.922 in MODEL 221 

ENGINE 273.923 in MODEL 164 

ENGINE 273.924 in MODEL 221 

ENGINE 273.943 in MODEL 164 

ENGINE 273.960 in MODEL 211, 219 

ENGINE 273.961 in MODEL 216, 221 

ENGINE 273.962 in MODEL 211 

ENGINE 273.963 in MODEL 164, 251 

ENGINE 273.965 in MODEL 230 

ENGINE 273.967 in MODEL 209 

ENGINE 273.968 in MODEL 221 

Shown on engine 272 

Fig 1: ME-SFI Lambda Control, Function (Shown On Engine 272)
G04738451Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

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 O2 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):

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 (STAR Diagnosis)
G04738454Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
  Component description for the ME-SFI [ME] control unit   GF07.61-P-6000V 
  Component description for the O2 sensors O2 sensors upstream of the TWC GF07.04-P-6100V
    O2 sensors downstream of the TWC GF07.04-P-6100VA
  Component description for the crankshaft Hall sensor   GF07.04-P-6220V
  O2 sensor heater, function   GF07.61-P-3025V 
  Component description for the hot film mass air flow sensor   GF07.07-P-6000V
  Component description for the coolant temperature sensor   GF07.04-P-6040V
  Self-adjustment of mixture formation, function   GF07.61-P-3030V 
  Component description for the accelerator pedal sensor   GF30.20-P-2010V
  Component description for the fuel injection valves   GF07.03-P-6010V
  ME-SFI two-sensor control, function   GF07.61-P-3020V 
  Component description for the three-way catalytic converter   GF49.10-P-2010V