"Dieselgate" might be winding up for Volkswagen, but investigations into diesel emissions cheating are just getting started elsewhere. Daimler is being investigated for alleged "fraud and criminal advertising" regarding Mercedes diesels, and the US Department of Justice has filed a civil suit against Fiat Chrysler for failing to correctly disclose emissions control devices in over 100,000 passenger cars with 3.0-liter EcoDiesel engines.

To understand what's going on with FCA, it's important to first explain a little bit about EPA rules regarding emissions control devices. It isn't illegal for manufacturers to bury less environmentally friendly drive modes within their engine control units (ECU) – they might need to run in less efficient, dirtier tune to protect the engine while towing or running off-road, for example – but these different tunes do need to be disclosed to testers.

This is to prove they aren't a "defeat device," hidden there to make the run car run more efficiently under test conditions. As you might imagine, any car with one of these devices can't be certified by the EPA. In the VW case, code buried within the ECU would detect when the car was in a controlled test environment and switch to a rule-meeting clean mode. When it was removed from this environment, it would default back to dirty (but more powerful and drivable) regular mode.

The US DOJ filing claims Fiat Chrysler didn't disclose eight emissions control devices that allowed the cars to meet nitrogen oxide (NOx) emission standards in the testing laboratory, before switching to dirtier mode (with much higher NOx emissions) during certain on-road conditions. This puts them in violation of the Clean Air Act.

Fiat Chrysler allegedly fitted almost 104,000 RAM 1500 and Jeep Grand Cherokees with the device between 2014 and 2016. In a statement the automaker says it is "disappointed" the DOJ has filed the suit and says it intends to retro-fit cars accused of being modified to cheat emissions tests with the emissions tune used in 2017 models.