Following Volkswagen’s 2015 admission that it had rigged engine software with “defeat devices” to cheat U.S. diesel tests, several European states launched investigations.
They found on-the-road nitrogen oxide (NOx) emissions more than 10 times above regulatory limits for some Opel, Renault and Fiat Chrysler models, and widespread use of devices that reduce or shut down exhaust treatment during normal use.
French prosecutors opened criminal probes into Volkswagen, Renault, PSA Group and Fiat Chrysler in 2016-17 that remain ongoing.
A Renault spokesman said the company could not comment on the latest report because it had not seen its findings.
“Renault vehicles are not equipped with defeat devices and are homologated in conformity with the regulations in force,” the spokesman said.
The study by ISAT, a French transport research institute, confirmed earlier findings that engine software in Renault’s Clio and Captur models shut down one form of emissions control outside a range of air temperatures covering official tests but not everyday use, Le Monde reported.
Another anti-pollution technology, the “NOx trap”, did not run cleaning cycles below speeds of 50 kilometers per hour (31 miles per hour), according to the French daily. Without such periodic purges, the filters become clogged and ineffective.