Emission (Lambda) Control For Models With Catalytic Converter

In order to maintain the optimum degree of efficiency of the catalytic converter, this system aims at achieving the ideal air-fuel mixture (lambda = 1) for combustion. A heated oxygen sensor is used for this purpose which measures the residual oxygen in the exhaust gas and transmits a corresponding voltage value to the control unit where the mixture ratio is correspondingly corrected, if necessary, by varying the ignition timing. In the event of failure of an oxygen sensor, the DME control unit assumes control with a fixed programmed substitute value (.45 volt). Since a temperature of approximately 572°F (300°C) is necessary for efficient operation of oxygen sensor power is supplied by way of one relay to both heating resistors in the oxygen sensors. The DME control unit I activates the relay. This relay is omitted in series production. On models without a relay for oxygen sensor heating, sensor heaters are activated directly by the EKP relay.