2003 3BMXV04.4LEV (745i & 745Li)

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 - After cold start, secondary air pump begins and secondary air valves open. Air is forced into outlet ports of engine, which mixes with engine gases. Throughout duration of secondary air pump running, mix of engine gases is controlled. Front oxygen sensors will measure exhaust lambda and therefore calculate secondary airflow rate. Measured secondary airflow rate is compared with secondary airflow rate model and quotient is obtained and used as relative secondary air volume. This volume is compared with failure secondary air threshold, then secondary air phase lambda compensation will begin. During this operation, condition of quality of engine mix pre-control will be checked to guarantee safety diagnostic. When lambda control is between preset limits and relative secondary airflow rate is showed to be too low, a failure of secondary air system is diagnosed. See Figure.