Unnamed sources have told Reuters that the US Department of Justice is currently examining whether the automotive supplier knew of or participated in Volkswagen's scheme to cheat its way past emissions testing for some of its diesel engined cars.
According to the news wire's sources, the US investigation is at an early stage and, so far, the department has yet to find any evidence of wrongdoing on Bosch's part.
Bosch supplied key components, including the EDC17 engine control module, for Volkswagen's EA189 diesel engine family. It's understood that the EDC17 unit controls engine operations, including how to deal with burnt fuel before it is discharged as exhaust.
The German automotive giant admitted in September this year that it had installed emissions testing defeat devices on almost half-a-million cars in the US market equipped with its 2.0-litre TDI motor. Worldwide, there are an estimated 11 million cars with affected EA189 engines, including almost 100,000 in Australia.
Volkswagen, Bosch and US Department of Justice refused to comment on the record to Reuters about this latest alleged investigation.
Bosch has previously told the news agency that it supplies components to car makers based on their specifications, and "how these components are calibrated and integrated into complete vehicle systems is the responsibility of each automaker".