Bosch under probe in US over Volkswagen cheating scandal: report

US authorities are investigating the likely complicity of German auto supplier Robert Bosch in Volkswagen AG's massive scheme to cheat US emission standards, reports quoting sources familiar with the matter said.

Bosch built key components in the diesel engine used in six Volkswagen models and one Audi model that the automaker has admitted to rigging to defeat emissions tests.

Federal prosecutors with the US Department of Justice are now examining whether Bosch, the world's largest auto supplier, knew or participated in Volkswagen's efforts to circumvent US diesel emissions tests, reports said.

Bosch provides the engine control module, called EDC17, and basic software for nearly all the four-cylinder diesel cars sold in North America, including by Volkswagen AG, BMW AG and Daimler AG's Mercedes-Benz. 

Those systems regulate how a vehicle cleans burned-up fuel before it is expelled as exhaust.

Volkswagen had the engine software modified to turn on the vehicle's emission control system when it was being tested in the lab, then turn it off when the vehicle was on the road, according to US regulators.

For authorities to bring charges against Bosch, they would have to prove the supplier knew that their technology was being used by Volkswagen to evade emissions requirements.

The probe is reported to be at an early stage and there is no indication that US prosecutors have found evidence of wrongdoing at Bosch.

Volkswagen has admitted to installing software that allowed its 2.0 litre diesel models to pass US clean air tests, while shutting off emissions control systems when its diesel cars are actually on the road.

Federal authorities are also investigating the level of involvement of VW officials in the cheating scheme, the report added.

It is also not clear what role Bosch played and how closely it worked with VW to modify the engine management software and how much it knew about VW's intentions to use software to cheat on emissions standards.

Germany-based Bosch was an early promoter of the 'clean diesel' technology adoption in the US market and the company has lobbied US lawmakers since at least 2005 for laws to promote advanced diesel technology.