Importance

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Abstract

An on-board diagnostic system and method for directly monitoring the efficiency of a catalyst having negligible oxygen storage capacity is provided. The monitoring system includes an oxygen sensor mounted at a first end of the conditioning catalyst, and an exhaust gas catalyst bypass. The oxygen sensor includes a first side and a second side. The first side detects oxygen levels in the exhaust gas at or near the first end of the catalyst and the second side detects oxygen levels at or near the second end of the catalyst. The oxygen sensor simultaneously compares exhaust gas from the first end of the catalyst to the exhaust gases from the second end of the catalyst. The oxygen sensor produces a voltage signal which is proportional to the difference in oxygen levels between the upstream gases and the downstream gases. The method of the present invention includes providing an oxygen sensor and an exhaust gas catalyst bypass; transferring exhaust gas via the exhaust gas catalyst bypass to a second side of the oxygen sensor; simultaneously detecting oxygen levels in the exhaust gas at the first side and the second side of the oxygen sensor; and producing a voltage which is directly proportional to the amount of oxygen converted over the catalyst.

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First Claim