12 00 ... Instructions For Welding Work (Overload Protection Of Control Units)

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2006 BMW M3, 2005 BMW M3, 2004 BMW M3, 2003 BMW M3, and 2002 BMW M3. However, it is still accessible from the selected car via links, so may be relevant.

When performing welding work on installed control units, to avoid any defects in the electronic control units, observe the following steps:

Observe instructions for disconnecting and connecting battery. See 12 00 ... INSTRUCTIONS FOR DISCONNECTING AND CONNECTING BATTERY .
Detach terminal of battery negative lead from car battery and second battery if fitted. Cover negative terminal posts.
If welding is to be performed near the battery/batteries, first remove battery/batteries from vehicle (flying sparks - combustion of explosive gas).
Fit return clamp on welding unit as close as possible to welding point (maximum distance approx. 1 m).
Never connect return clamp to ground pin on body which has ground wires attached!