GF07.61-P-4022MLK ME-SFI Lambda Control, Function

GF07.61-P-4022MLK ME-SFI Lambda Control, Function
- refinement package
- as of model year 09


Function requirements for lambda regulation, general points
^ Circuit 87M ON (engine control ON)
^ Engine running
^ Coolant temperature >52 °C
^ Operating temperature reached in the LH and RH O2 sensors upstream of CAT (G3/3, G3/4)
^ Engine idling or partial-load range
^ Deceleration fuel shutoff not active.

Lambda regulation, general points
The mixture composition is controlled within the narrowest limits around lambda= 1 in order to achieve high conversion of the exhaust gases (exhaust gas conversion) in the catalytic converters.

For this purpose, the ME-SFI control unit (N3/10) reads the following sensors:
- Hot film MAF sensor (B2/5), engine load
- Coolant temperature sensor (B11/4)
- LH O2 sensor upstream of CAT, oxygen sensor signal
- RH O2 sensor upstream of CAT, oxygen sensor signal

Lambda regulation function sequence
The O2 sensors upstream of the CAT react to the proportion of oxygen in the exhaust gas and send the corresponding voltage signals to the ME-SFI control unit. The control unit then varies the mixture composition by adjusting the injection time of the fuel injection valves (Y62) so that lambda=1 is reached. 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.

Component Identification:

Example:
Assuming a leaner fuel-air mixture is produced. This has the consequences that the oxygen sensor voltage drops and the ME-SFI control unit compensates for the leaner mixture by enriching it accordingly (extending the injection time).
This makes it possible to achieve a fuel-air mixture of approximately lambda= 1.
The readout of the lambda control factor with the DAS alters in the direction +25%.
The more the lambda control factor moves in the direction +25%, the leaner is the fuel-air mixture and the greater is the enrichment of the mixture on the part of the ME control unit.