Wheel-Slip Control System:

WARNING: This page is about a different car, the 2007 BMW 550i, 2006 BMW 550i, 2005 BMW 545i, and 2004 BMW 545i. However, it is still accessible from the selected car via links, so may be relevant.

The slip control system is basically maintenance-free.

However, be sure to adhere to the following:

When carrying out welding work with electric welding equipment, be sure to disconnect the plug from the electronic control unit (ignition turned off).
During painting work, the control unit may be subjected for brief periods to loads of max. 95° C and for long periods (approx. 2 hours) to loads of max. 85° C.
Tighten down the battery terminals completely.
The brake lines on the hydraulic unit must not be mixed up; if necessary, mark them before they are removed and after completing repairs perform the mix-up check with the DIS Tester.