Catalytic Converter Monitoring

Catalyst Monitoring is performed by the EMS2000 under oxygen sensor closed loop operation. The changing air/fuel ratio in the exhaust gas results in lambda oscillations at the pre-catalyst sensor. These oscillations are dampened by the oxygen storage activity of the catalysts and are reflected at the post catalyst sensor as a fairly stable signal (indicating oxygen has been consumed). Conditions for Catalyst Monitoring:

Catalyst temperature is a theoretical calculation performed by the EMS2000 that is a function of load/air mass and time.

As part of the monitoring process, the pre and post O2 sensor signals are evaluated by the EMS2000 to determine the length of time each sensor is operating in the rich and lean range.

If the catalyst is defective the post O2 sensor signal will reflect the pre O2 sensor signal (minus a phase shift/time delay), since the catalyst is no longer able to store oxygen. The catalyst monitoring process is stopped once the predetermined number of cycles are completed, until the engine is shut-off and started again. After completing the next "customer driving cycle" whereby the specific conditions are met and a fault is again set, the "Malfunction Indicator Light" will be illuminated.