2003 3BMXV02.5M56
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- General Description - Catalyst monitoring is based on monitoring its oxygen storage capability. Engine closed loop feedback control generates lambda (air/fuel ratio) oscillations in exhaust gas. These oscillations are dampened by oxygen storage activity of catalyst. Amplitude of remaining lambda oscillations downstream of catalyst indicates storage capability.
- Monitoring Procedure - To determine catalyst efficiency, model-based nominal amplitude of upstream oxygen sensor is modified to predefined higher values (forced stimulated). This results into a known area of A/F controller, whereby magnitude of oxygen admission to catalyst converter is equal independently to driving conditions. Magnitude of oxygen admission is used to calculate maximum permissible oscillation (areas of cycle) of downstream sensor of a still good working catalyst. See Fig 1-Fig 3 .