Emission Management: Notes

As soon as the engine has started a pulse width modulated ground signal from the EMS2000 is supplied to the Oxygen Sensor Heaters. Duty cycle is increased to approximately 98% until the O2 sensors are fully heated. Afterwards the duty cycle is varied to maintain temperature of the sensors. During engine deceleration the duty cycle is increased to compensate for the decrease in exhaust temperatures.

Once heated fully the O2 sensors provide information about oxygen content in the exhaust. The EMS2000 makes trim adjustment to the injector on time based on the input from the pre - O2 sensor. The post O2 sensor is used for monitoring catalyst condition.

A high voltage reading from the pre - O2 sensor indicates a lack of oxygen in the exhaust or a rich mixture. The EMS2000 will reduce injector on time until the voltage reading drops at which time the on time will be increased again.