Abstract: In a fuel management system for an internal combustion engine, a system utilizing a stoichiometric gas sensor in the exhaust gas system for supplying an electrical signal to an asymmetrical integrator which controls and maintains any desired air/fuel ratio to the engine. By means of the system, the air/fuel ratio may be maintained slightly richer than stoichiometric for optimum catalytic converter operation. For very lean air/fuel ratios, a delay circuit is used in the system to continue the time the fuel mixture is in a lean condition before the mixture is controllably changed to a rich mixture for sensing by the sensor.

Abstract: In a fuel management system of an internal combustion engine having an exhaust gas sensor positioned in the exhaust gases of the engine for controlling the fuel mixture to the engine, an exhaust gas sensor failure detection system for determining when the sensor fails to respond within a given time period to a rich to lean fuel mixture transition. The sensor in response to a rich fuel mixture generates a high voltage output which is switched to a low voltage output when the fuel mixture goes lean. The time of transition is used as an indication of the quality and performance of the exhaust gas sensor.