The IG Metall union, which represents workers, has criticised the process, according to Auto Motor Und Sport magazine. The division is profitable and has met its targets.
A union spokesperson said it was difficult to understand why Siemens would want to separate the company out when it had only been fully integrated into Siemens AG during 2006.
Workers are reported to be demotivated by the events and by plans to reduce the 50,000-strong workforce by 1,000.
Siemens said last month that it would float some of the Siemens VDO division, but retain a controlling interest in the company. Since then it has received enquiries from at least two of its major competitors considering acquiring the division – TRW and Continental.
Indeed, Siemens may now be obliged to pursue a full sale of the company if that is in the interest of shareholders.