According to the Bild am Sonntag, the German Motor Transport Authority (KBA) believes that the device allows the car's emissions control system to work optimally for around 22 minutes before shutting off. Just enough time for it to pass a German emissions test, which typically runs for around 20 minutes.
Fiat Chrysler was summoned to a meeting in the middle of May with the KBA to discuss these allegations.
Alexander Dobrindt, Germany's transport minister, told Reuters and other agencies that the car maker cancelled at the last minute and instead sent a letter from its lawyers.
"This uncooperative behavior of Fiat is completely incomprehensible," the minister said in a statement. "It would be appropriate if Fiat would take a stand on this in front of the investigating committee."
Above: Fiat 500X.
Lawyers for the Italian-American car maker have reportedly asserted that as its vehicles are approved by the Italian authorities, the KBA should direct its inquiries to its Italian counterpart, who then, presumably, will chase up the matter with Fiat Chrysler if required.
This is a view that Graziano Delrio, Italy's transport minister, shares and has conveyed this to the German government. Fiat Chrysler has made no official comment about these allegations.
Investigations into potential cheating of emissions testing were launched by a number of European countries after Volkswagen admitted to installing defeat devices on cars fitted with its EA189 diesel engine in September 2015.