GF49.10-P-3033CY Catalytic Converter Efficiency Monitoring Function

GF49.10-P-3033CY Catalytic Converter Efficiency Monitoring Function
ENGINE 272.911 in MODEL 204.0 up to Model Year 8
ENGINE 272.921 in MODEL 204.0 /2 up to Model Year 8
ENGINE 272.947 in MODEL 204.0 /2 up to Model Year 8
ENGINE 272.948 in MODEL 204.0 up to Model Year 8
ENGINE 272.961 in MODEL 204.0 /2 up to Model Year 8
ENGINE 272.971 in MODEL 204.0 up to Model Year 8

The firewall catalytic converters are assessed concerning their capacity to store oxygen. The oxygen stored during a lean phase is totally or partially reduced during the rich phases. Aging causes downsizing of the oxygen storage capacity of firewall catalytic converters. This aging also causes reduction in the HC conversion.

Changes in the oxygen content downstream of the firewall catalytic converters are almost completely dampened by the high oxygen storage capacity of the firewall catalytic converters.

This results in the oxygen sensor signal downstream of the firewall catalytic converters being virtually constant with a small amplitude.

By law, HC emissions must not go above certain limits. The task of monitoring of firewall catalytic converter is to obtain a statement from the oxygen storage capacity of the firewall catalytic converters about their aging and thus about HC conversion.

When the firewall catalytic converter is operationally warm and lambda control enabled, the amplitude sizes of the oxygen sensor signals upstream and downstream of the firewall catalytic converters are compared.

If the firewall catalytic converter is no longer operational, the oxygen sensor signal upstream and downstream of the firewall catalytic converters will be equal.
Within the specified engine rpm range a number of measurements take place in the lower partial-load range.

During the first stage, the oxygen stored when the mixture is rich (lambda about 0.95) is reduced until the sensor voltage downstream of the catalytic converter is greater than about 650 mV.

In the second operation step there is switchover to a lean mixture (lambda about 1.05) and monitoring takes place to see how long it takes until the sensor voltage downstream of catalytic converter is less than about 200 mV.

If the length of time measured is below a stored characteristic in the ME-SFI [ME] control unit (N3/10) set as the borderline characteristic for catalytic converters, then oxygen storage capacity is insufficient and the firewall catalytic converter must be replaced.
Recognized faults are stored in the fault memory by the ME-SFI [ME] control unit and can be read out and deleted using the DAS.

In the event of fault detection, the engine diagnosis indicator lamp lights (A1e58) up in the instrument cluster (A1).