GF07.61-P-3020F | ME-SFI two-sensor control, function | 20.3.08 |
ENGINES 104.941 /943 /944 /991 /994 as of 1.8.96 with CODE (494) USA version
ENGINES 104.995 with CODE (494) USA version
ENGINES 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 (494) USA version
ENGINES 111.945
in model 202.020 /080 as of 1.9.98,
208.335 /435 as of 1.6.98 with CODE (494) USA version
ENGINES 111.952 /956 /957 /958 /982 /983
ENGINES 111.974, 112.970 /972 with CODE (494) USA version
ENGINES 112.910 /911 /912 /913 /914 /917 /920 /921 /922 /923 /940 /941 /942 /943 /944 /947 /949 /954 /955 /975
with CODE (925) Low emission EURO3
with CODE (926) Low emission EURO4
with CODE (494) USA version
ENGINES 113.940 /941 /942 /943 /948 /960 /961 /965 /966 /967 /968 /969
with CODE (925) Low emission EURO3
with CODE (926) Low emission EURO4
with CODE (494) USA version
ENGINES 119.980 /981 /982 /985 with CODE (494) USA version
ENGINES 120.982 /983 with CODE (494) USA version
ENGINES 137.970
ENGINES 111.951 /955 up to Model Year 08 /Modification Year 07
ENGINES 112.916 /946 /953 /973
with CODE (926) Low emission EURO4
with CODE (494) USA version
up to Model Year 08 /modification year 07
ENGINES 113.963
with CODE (925) Low emission EURO3
with CODE (926) Low emission EURO4
with CODE (494) USA version
up to Model Year 08 /modification year 07
Task
Improving the stability of the lambda control.
Monitoring O2 sensor upstream of TWC.
Engine
Lambda control
Catalytic converter
Monitoring
Cycle duration
Monitoring
Limit values
O2 sensor
upstream TWC
O2 sensor
downstream TWC
Correction variable for lambda closed-loop control
Specified/actual value comparison
P07.61-0383-06
1 O2 sensor signal upstream of TWC
a Voltage threshold for
b Rich - lean transition
c Lean - rich transition
2 Lambda control without correction variable
3 Lambda control with
correction variable (d), timing variation
(+TV) in rich direction
4 Lambda control with
correction variable (e), timing variation
(-TV) in lean direction
The engine control unit determines the lambda mean value from signals from the O2 sensors 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 O2 sensor upstream of 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 therefore a two-sensor control is not possible either.
The effect of the firewall catalytic converters is monitored based on the O2 sensor signals downstream of the TWC.