Multiple anonymous sources both within the carmaker and close to on-going investigations have told Reuters that Volkswagen needed to update or rewrite its software to accommodate different versions of the affected turbo-diesel family.
Officials from the automaker refused to comment on the record to the newswire, except to say: "We are working intensely to investigate who knew what and when, but it's far too early to tell."
Earlier this month, Michael Horn, the company's American chief, told a televised congressional committee hearing that "to my understanding, this was not a corporate decision, this was something individuals did".
He also stated that while it is "very hard to believe", to his knowledge the work was down to a "couple of software engineers who put this in for whatever reason". A report in German media over the weekend claimed that at least 30 managers were involved in the, so-called, "dieselgate" affair.
In mid-September, the Volkswagen Group admitted that it had installed software in some of its turbo-diesel cars, which could detect when it was in a laboratory for emissions testing and generate compliant results.
It's estimated that up 11 million vehicles worldwide — almost 100,000 of them in Australia — have this cheat code installed. The local arms of Volkswagen and Audi have temporarily halted sales of cars with the suspect EA189 engines, and setup websites for owners to see if they affected.
The company is currently working on making impacted vehicles compliant, but cars won't start heading back to dealership until early 2016, at the earliest. Depending on the car concerned, the required update may involve either a software, or a software and hardware fix. Horn admitted that, in some cases, at least, there will be a slight performance impact.