Normally, there is an automated test in the scan tool for this system. You just run the test and watch the data, but for whatever reason the test was not available on this vehicle. You can run into some challenges depending on how you try to do a manual test.

I won't list all of the things that can get in your way here. Lets just skip to the easier way to go about testing this system manually. Access the proper pin at the ECM that controls the air pump relay. The ECM is easy to access under the e-box cover in the engine compartment. The secondary air valve on this vehicle is opened from the pressure of the air pump, but some older BMW's use a vacuum actuated air valve, so on those you will need to use a vacuum pump to open the air valve.

The ECM uses the front O2 sensor voltages to monitor the sec. air flow. If there is lots of flow, then the O2 sensor voltages will be zero volts. Use a scan tool that can graph the front O2 sensor voltages during your manual test. Here's a sample image:

[2002 BMW M3, Emissions Scan Data]

Steven McGrew
Technician
European AutoHaus
Spokane, Washington, USA

Files Referenced: