2003 3BMXV03.2S54 & 3BMXV04.9S62

WARNING: This page does not describe the selected car, but rather 18 other vehicles, including the 2002 BMW Z8, 2002 BMW Z3, 2002 BMW X5, 2002 BMW M5, and 2002 BMW M3. However, it is still accessible from the selected car via links, so may be relevant.

General Description Of Secondary Air System Monitoring - At cold start, secondary air pump and valve are switched on for their normal operating function. Secondary air delivered into exhaust gas is causing a lean mixture indicated by output voltage of oxygen sensor. Anytime oxygen sensor indicates a rich mixture (voltage greater than a fixed limit) within a predetermined time range and calculation of relative secondary air mass is less than a defined threshold, it seems like a faulty secondary air system. Now a correction procedure follows immediately, after secondary air system is switched off. Air/fuel influence is determined by deviation of lambda-controller. If influence is less than a fixed threshold, finally a fault will be detected. If influence is greater than a fixed threshold, results of diagnosis will be rejected as long as a lean mixture (voltage less than a fixed limit) is indicated from oxygen sensor within a predetermined time range and correction of air/fuel influence (after secondary air pump shuts-off) is less than a fixed threshold, a fault will also be detected. See Figure.