C 350 (204.056) V6-3.5L (272.961) (2008)
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Engine Control Module: Description and Operation
GF07.61-P-4022CY ME-SFI Lambda Control, Function
GF07.61-P-4022CY ME-SFI Lambda Control, Function
- up to model year 08
The mixture composition is controlled within the narrowest possible limits around lambda= 1 in order to achieve a high conversion of the exhaust gases
(exhaust gas conversion) in the catalytic converters.
Oxygen sensors on the left and right upstream of the TWC (G3/3, G3/4) react to the oxygen portion in exhaust gas and send appropriate voltage signals
to the ME-SFI [ME] control unit (N3/10). Consequently, the mixture composition is modified by control of the injection quantity, so that lambda=1 is
obtained. This process is repeated constantly (control loop).
The ME-SFI [ME] control unit alters the mixture composition with a time delay in order to prevent any risk of jerking.
Control of the air/fuel ratio is much faster by using a wideband oxygen sensor (continuous signal of lambda 0.7 to 4.0) than an oxygen sensor upstream
of TWC.
The function of the lambda control (closed-loop operation) is dependent upon:
^
Coolant temperature >-10 °C
^
Blocking time after starting expired
^
Operating temperature of the oxygen sensors upstream of catalytic converter
^
Engine idling or partial-load range
^
Deceleration fuel shutoff not active.
Component Identification
Example:
Assuming a leaner fuel-air mixture is produced. This has the following consequence, that the The oxygen sensor voltage drops and the ME-SFI [ME]
control unit compensates for this lean drift by making a matching enrichment. This makes it possible to achieve a fuel-air mixture of approximately
lambda= 1.
Readout of the lambda control factor with the DAS alters in the direction +25%.
