Fiat Chrysler has become the latest carmarker to be dragged into the emissions scandal.
US regulators have alleged thousands of its jeeps and trucks contained emissions-manipulating software that was not disclosed to the authorities.
The US Environmental Protection Agency said the software is present inside 104,000 Jeep Grand Cherokee and Dodge Ram trucks.
It said Fiat Chrysler could be liable for fines of US$44,500 per vehicle, or about US$4.6 billion (NZ$6.45 billion).
Volkswagen was recently fined a similar amount over its emissions cheating.
Watch the Channel 4 report for the full story.