Monitoring function

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2008 BMW Z4, 2008 BMW X5, 2008 BMW X3, 2008 BMW 528xi, and 2008 BMW 528i. However, it is still accessible from the selected car via links, so may be relevant.

If all monitoring conditions are fulfilled, then a special defined A/F-modulation will be done.

The first lean to rich cycle of the test is only used to establish an average voltage value of the downstream sensor voltage. During subsequent cycles the calculation of the OSC is based on the accumulated value of the difference between the average value of the previous lean to rich cycle and the measured instantaneous voltage during the current lean to rich cycle.

The relation of the deviation between the current downstream-sensor-signal to the average value of the downstream-sensor-signal is a lead for catalyst condition. The catalyst system is considered malfunctioning, if after a specified number of monitoring cycles the average of the accumulated deviation exceeds a threshold. The corresponding fault code is stored.