In order to maintain optimum efficiency of the catalytic converters, the system endeavours to provide the ideal air-fuel mixture ratio (Lambda = 1) for combustion.The system features 2 heated oxygen sensors (1 for each row of cylinders with relevant exhaust gas line = Stereo lambda control) which measure the residual oxygen in the exhaust gas and send corresponding voltage values to the control unit. Here, if necessary, the mixture composition is corrected accordingly in that the injection timing is varies. In the event of the oxygen sensor failing, the DME control unit takes over control with a fixed programmed substitute value (0.45 V).
Since the oxygen sensors require a temperature of approx. 300 degrees Centigrade in order to operate efficiently, voltage is supplied to the heating resistors in the oxygen sensors via a relay.The DME control unit controls relay activation.