Attorneys representing thousands of VW car owners filed a 742-page brief in U.S. District Court in San Francisco last week that cites confidential documents which are prompting investigators to look into auto-parts supplier Robert Bosch GmbH 's involvement in VW's rigged emissions tests. Bosch supplied VW with engine control units for the German automaker's vehicles and, according to the Fortune report, attorneys wrote, “It is inconceivable that Bosch did not know that the software it was responsible for defining, developing, testing, maintaining and delivering contained an illegal defeat device.”
Bosch’s electronic diesel control unit, called the EDC Unit 17, contains specific algorithms to adjust fuel levels, air pressure, recirculation of exhaust gas to lower NOx emissions, and injection rates of urea, the fluid used to break down NOx into harmless component parts before it is emitted from a car’s tail pipe. EDC Unit 17 also is used on diesel vehicles from several manufacturers, including Volkswagen, BMW AG and Daimler AG ’s Mercedes-Benz.
A study conducted by the German government concluded earlier this year that most manufacturers were using software to manipulate toxic emissions from the diesel vehicles, although Volkswagen appeared to be the only one to install test recognition software.