Test Group YBMXV03.2S52
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- Catalyst Monitoring General Description - Catalyst monitoring is based on monitoring catalyst's oxygen storage capability. The engine closed loop feedback control generates lambda (air/fuel ratio) oscillations in the exhaust gas. These oscillations are dampened by the oxygen storage activity of the catalyst. The amplitude of the remaining lambda oscillations downstream of the catalyst indicates the storage capability.
- Monitoring Procedure -
The conversion efficiency of both catalyst systems (Cyl. 1-3 and Cyl. 4-6) are separately monitored. In order to determine the efficiency, lean and rich time periods of the oxygen sensors up and downstream will be compared. See Fig 1-Fig 3
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The smaller of the two ratios is used for further processing. The cycle counter is incremented by one after each cycle. If the counter reaches a predetermined number of checks, and the sum of all ratios determined is greater than a fixed value, a fault will be stored in computer memory. The monitoring procedure is then terminated until the engine is shut-off and started again.