Oxygen Sensor Heating
Oxygen sensor heating is an output function of the MS S52 control module. The heating circuits receive operating power from the main relay when KL 15 is switched on. Each of the heaters is controlled through a separate final stage which is monitored by the control module for OBD II purposes.
The heaters are controlled with a pulsed square wave voltage during cold start which allows heating to occur without the result of thermo-shock. The duty cycle is then varied to maintain the heating of the sensors. On decel, the duty cycle will be increased to maintain the heating of the sensors during closed throttle operation with fuel cut.