ME-SFI two-sensor control function - GF07.61-P-3020F

ENGINE 104.941 /943 /944 /991 /994 as of 1.8.96 with CODE (494a) USA version

ENGINE 104.995 with CODE (494a) USA version

ENGINE 111.921 /942 as of 1.9.98,

111.943,

111.944 as of 1.8.96,

111.946 as of 1.6.98,

111.947/973,

111.975 as of 1.8.96 with CODE (494a) USA version

ENGINE 111.945

in MODEL 202.020 /080 as of 1.9.98,

208.335 /435 as of 1.6.98 with CODE (494a) USA version

ENGINE 111.951 /952 /955 /956 /957 /958 /982 /983

ENGINE 111.974,112.970 /972 with CODE (494a) USA version

ENGINE 112.910 /911 /912 /913 /914 /916 /917 /920 /921 /922 /923 /940 /941 /942 /943 /944 /946 /947 /949 /953 /954 /955 /973 /975

with CODE (925) low emission EURO3

with CODE (926) low emission EURO4

with CODE (494a) USA version

ENGINE 113.940 /941 /942 /943 /948 /960 /961 /963 /965 /966 /967 /968 /969

with CODE (925) low emissionEURO3

with CODE (926) low emissionEURO4

with CODE (494a) USA version

ENGINE 119.980/981 /982 /985 with CODE (494a) USA version

ENGINE 120.982 /983 with CODE (494a) USA version

ENGINE 137.970

Task

Improving the stability of the lambda control.
Monitoring the O₂ sensor upstream of TWC

Fig 1: ME-SFI Two-Sensor Control Function - Flow Chart

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Fig 2: O2 Sensor Signal Upstream Of TWC Graph

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

The engine control unit calculates the lambda mean value from the signals supplied by the oxygen sensor downstream of TWC. This value is compared with a stored value for optimum exhaust emissions.

If the variation of several measurements is too large, a correction variable (lag time ± TV) is determined for the lambda control.

Use of the correction factor (value for a new O₂ probe about 0) allows one to compensate for aging of the O₂ probe upstream of the catalytic converter within certain limits. If the correction variable exceeds the limit value, the oxygen sensor upstream of the TWC must be replaced.

In addition, allowance is made for the period of the signal supplied by the sensor upstream of TWC. If no sensor state change takes place, the lambda control is not active and no two-sensor control is therefore possible either.

The effect of the three-way catalytic converter is monitored with the oxygen sensor signals downstream of TWC.

Motor electronics control unit, location/task/ design/function	other than engine 111 EVO	GF07.61-P-5000F
	Engine 111 EVO	GF07.61-P-5000GS
O sensors, location/task/design/function		GF07.04-P-4103F
Three-way catalytic converter location/task/ design/function		GF49.10-P-3002F