GF07.61-P-3020MIK ME-SFI Two-Sensor Control, Function

GF07.61-P-3020MIK ME-SFI Two-sensor Control, Function
- refinement package
- as of model year 09


Function requirements for two-sensor control, general points
^ Circuit 87M ON (engine control ON)
^ Engine running
^ Operating temperature of firewall catalytic converters is reached
^ Lambda regulation active
^ Left and right O2 sensors downstream of CAT (G3/5, G3/6) defect-free

Two-sensor control, general points
The two-sensor control system is used to monitor the operation of the LH and RH O2 sensors upstream of CAT (G3/3, G3/4) and the effectiveness of the firewall catalytic converters.

To do this, the ME-SFI control unit (N3/10) reads the following sensors:
- LH and RH O2 sensors upstream of CAT, oxygen sensor signals
- LH and RH O2 sensors downstream of CAT, oxygen sensor signals

Two-sensor control function sequence
The ME-SFI control unit determines the lambda mean value using the signals from the oxygen sensors downstream of the CAT. 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.

The correction value (value with new LH and RH O2 sensors upstream of the CAT is about 0) is used to compensate for aging of the O2 sensors upstream of CAT, within certain limits.

If the correction value exceeds the specified limit value, the O2 sensors upstream of CAT must be replaced.
The correction value depends on the performance map, and ME-SFI control unit applies it by adjusting the injection time of the injection valves (Y62).

If the specified limit value is exceeded, or the plausibility check on the oxygen sensor signals (upstream or downstream of CAT) is negative, the ME-SFI control unit actuates the engine diagnosis indicator lamp on the instrument cluster (A1) (A1e58) (or with code (494) USA version, the CHECK ENGINE indicator lamp (A1e26)) over the engine compartment CAN (CAN C).

The exceeded limit value is stored in the fault memory by the ME-SFI control unit and can be read out and deleted using the DAS system.