LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Mercedes Benz >> 2021 >> Sprinter 1500 Van Cargo >> Repair and Diagnosis >> Engine Performance >> System >> Mixture Formation - Description & Operation, General Information, Basic Knowledge, Safety Precautions >> Basic Knowledge >> Lambda Control, Function - GF07.10-D-1010TSB
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Lambda Control, Function - GF07.10-D-1010TSB

Engine 274 in model 907 

Block diagram 

G13786490

Function requirements for lambda control, general points 

Lambda control, general points 

To achieve a high exhaust gas conversion in the catalytic converter (three-way catalytic converter), the mixture composition is regulated in narrow limits around the air/fuel ratio (λ) = 1.

To do this the ME-SFI [ME] control unit reads in the following signals:

Exhaust conversion in catalytic converter (for engine with homogeneous mode) 

G13786491

Function sequence for lambda control 

Lambda control is described in the following points:

Function sequence for closed-loop control circuit 

The sensor element for the oxygen sensor upstream of the catalytic converter responds to the oxygen content in the exhaust and sends corresponding signals to the ME-SFI [ME] control unit.

In the case of low oxygen content (λ < 1) in the exhaust gas, the sensor element of the lambda sensor upstream of the catalytic converter transmits the "Rich mixture" signal to the ME-SFI [ME] control unit. This then reduces the injection quantity by regulating the fuel injectors and changes the mixture composition in the direction "lean". The oxygen content in the exhaust increases and the value alters in the direction λ = 1.

In the case of high oxygen content (λ > 1) in the exhaust gas, the sensor element of the lambda sensor upstream of the catalytic converter transmits the "Lean mixture" signal to the ME-SFI [ME] control unit. This then increases the injection quantity through regulation of the fuel injectors and alters the mixture composition in the direction "rich". The oxygen content in the exhaust decreases and the value alters in the direction λ = 1.

This process is repeated (control loop). The ME-SFI control unit alters the mixture composition with a time delay in order to prevent any risk of jerking.

IMPORTANT The control status is displayed in XENTRY Diagnosis by means of a lambda control factor that changes in the positive direction in the case of mixture leaning and in the negative direction in the case of mixture enrichment.

Additional function requirements for two-sensor control 

Function sequence for two-sensor control 

The two-sensor control monitors the oxygen sensor upstream of the catalytic converter function and the catalytic converter efficiency. To do this the ME-SFI [ME] control unit reads in the following signals:

The ME-SFI [ME] control unit uses the signals from the sensor element for the oxygen sensor downstream of the catalytic converter to determine the lambda mean value. This value is compared with a stored value for optimum exhaust emissions.

If the deviation is too large after a number of measurements, a correction value is determined for the lambda control. Using the correction value, the aging of the lambda sensor upstream of the catalytic converter in compensated for within certain limits.

IMPORTANT The correction value for a new lambda sensor upstream of the catalytic converter is approx. 0.

The correction value depends on the performance map and the ME-SFI control unit applies it by adaptation of the injection period of the fuel injectors. If it exceeds the specified limit value and the following fault cases are excluded for the mixture formation, the lambda sensor upstream of the catalytic converter must be replaced.

The following faults can, for example, occur during mixture formation:

If the specified limit value is exceeded or if the plausibility test for the lambda sensor signals (upstream or downstream of the catalytic converter) is negative, the ME-SFI [ME] control unit actuates the indicator symbols in the instrument cluster via the drive CAN, powertrain control unit, suspension FlexRay, EZS control unit and the user interface CAN.

Exceeding of the limit value is stored in the fault memory by the ME-SFI [ME] control unit and can be read out and deleted using the Xentry Diagnostics.

Function sequence for lambda sensor heater 

The lambda sensor heaters downstream and upstream of the catalytic converter bring the lambda sensor more quickly to operating temperature. With a controlled heater, they also prevent damage to the oxygen sensor ceramics.

When the exhaust system is very cold (while condensation is present), the oxygen sensors heaters downstream and upstream of the catalytic converter are switched off to prevent damage (due to thermal shock).

Additional function requirements self-adjustment of the mixture formation 

Function sequence for self-adjustment of the mixture formation 

For regulated catalytic converters, the lambda control determines the injection period so exactly that a specified air/fuel ratio (λ) is maintained under all operating conditions.

Self-adjustment ensures that the mixture composition in the open-loop operation (e.g. warm-up) is neither too rich nor too lean. It also prevents the lambda control from coming to the end stop at high altitudes.

If a fault occurs, the ME-SFI [ME] control unit automatically makes a correction of the mixture formation. In this case, the lambda characteristics map is shifted within the specified control limits so that the lambda control is not at the upper or lower end stop.

Shifting of the lambda characteristics map 

G13786492

If the mixture composition is constantly drifting out of the center controlled range, the ME-SFI [ME] control unit shifts under certain operating conditions the lambda characteristics map until the lambda control factor is again approx. 0.

Shown with self-adjustment value with Xentry diagnostics 

The following can be read out with Xentry diagnostics:

Presentation takes place in the form of a factor and means that the measured air mass value is multiplied by the factor. Example:

Additional function requirements for catalytic converter monitoring 

Catalytic converter monitoring, general points 

The law maker requires that the hydrocarbon emissions do not exceed a certain value. It is therefore necessary to constantly check the catalytic converter for aging. Aging of a catalytic converter is caused by the reduction of oxygen storage capacity over time and the resulting decrease in hydrocarbon conversion. The catalytic converter stores oxygen during mixture leaning (closed-loop control circuit) and releases it again during enrichment of the mixture for hydrocarbon conversion.

Function sequence for catalytic converter monitoring 

To check the oxygen storage capacity, a rich mixture (λ < 1) is output until the lambda sensor downstream of the catalytic converter has reached a specific maximum value and the majority of the oxygen has been depleted.

A lean mixture (λ > 1) is then output, and the time is measured to see how long it takes until the oxygen sensor downstream of the catalytic converter has reached a certain minimum value and the catalytic converter has filled up its oxygen storage capacity.

If the time measured lies below a stored characteristic, then the oxygen storage capacity is inadequate and an error is stored in the ME-SFI control unit.

Electrical function schematic for lambda control PE07.10-D-2710-97TSA
Overview of system components for gasoline injection and ignition system with direct injection GF07.70-D-9998TSB 
scientia non olet · About LEMON Manuals