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

ENGINE 275.950 in MODEL 215, 220

ENGINE 275.951 in MODEL 230

ENGINE 275.953 in MODEL 216, 221

ENGINE 275.954 in MODEL 230

ENGINE 275.980 in MODEL 215, 220

ENGINE 275.981 in MODEL 230

ENGINE 275.982 in MODEL 216, 221

ENGINE 285.950 in MODEL 240

ENGINE 285.980 in MODEL 240

Fig 1: ME-SFI Two-Sensor Control Function Diagram

The two-sensor control has the following tasks:

Assure long-term stability of the lambda control
Monitoring O₂ sensors upstream of TWC
Monitoring efficiency of catalytic converters.

Fig 2: ME-SFI Two-Sensor Control Function Diagram

Fig 3: O2 Sensor Signal Upstream Of TWC Graph

The ME engine control unit determines the lambda mean value from the signals of the O₂ sensors downstream of TWC. 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 variable (time delay ± T_V ) is determined for the lambda control.

The correction variable (value for new O₂ sensor approx. 0) makes it possible to compensate for aging of the O₂ sensor upstream of TWC within certain limits. If the correction variable exceeds the limit value, the O₂ sensor upstream of the TWC must be replaced.

The correction values are map-controlled and are implemented by the ME-SFI [ME] control unit by adapting the fuel injection.

Furthermore, 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.

In case of error the engine diagnosis indicator lamp lights up or for the CHECK ENGINE indicator lamp in the instrument cluster and a fault is stored in the fault memory.

The stored faults can be read out and erased with the DAS.

ME-SFI [ME] control unit, location/task/design/function		GF07.61-P-5000M
O₂ sensors, location/task/design/function		GF07.04-P-4103M
Three-way catalytic converter, location/task/design/function		GF49.10-P-3002M
"CHECK ENGINE" indicator lamp, location/task/function	At	GF54.30-P-4101M
Engine diagnosis indicator lamp, location/task/function	except	GF54.30-P-4102M
Fuel injection valve, location/task/design/function		GF07.03-P-5004M