C 240 Wagon (203.261) V6-2.6L (112.912) (2003)
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), time delay (+TV) in rich direction
4
Lambda control with correction variable (e), time delay (-TV) in lean direction
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.
Note: The effect of the three-way catalytic converter is monitored with the oxygen sensor signals downstream of TWC.
GF07.04-P-4103-01F O2 Sensors Function
GF07.04-P-4103-01F O2 Sensors Function
The sensor ceramic is conductive for oxygen ions from approx. 300 degrees C. If the oxygen share varies greatly on both sides of the ceramic probe
body, a voltage (Nernst concentration cell) is generated on the friction planes by means of the particular properties of the ceramic probe body on the
friction plane. This is a measure for the residual oxygen content in the exhaust.