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

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

Component Identification:

Function requirements for lambda regulation, general points
^ Circuit 87M ON (engine control ON)
^ Engine running
^ Coolant temperature >52 °C
^ Operating temperature reached in 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:
- Coolant temperature sensor (B11/4)
- Charge air temperature sensor (B17/8) and pressure sensor downstream of throttle valve actuator (B28/7), engine load
- LH and RH O2 sensors upstream of CAT, oxygen sensor signals

Lambda regulation function sequence
The O2 sensors upstream of the CAT react to the oxygen content in the exhaust and send the corresponding voltage signals to the ME SFI control unit. This then regulates 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.







Example:
Assuming a leaner fuel-air mixture is produced. This has the consequences that the oxygen sensor voltage drops and the MESFI 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 lambda control factor indicated with the Diagnosis Assistance System (DAS) changes towards +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.