French prosecutors open formal probe into PSA Group diesel emissions

French prosecutors have opened a formal investigation into suspected diesel emissions test-cheating by PSA Group , the maker of Peugeot and Citroen cars, a judicial source said on Monday.The company is being investigated for alleged consumer fraud offences, the source said.In February, Paris-based PSA became the fourth carmaker to be referred to prosecutors by France's DGCCRF consumer fraud watchdog over suspected diesel test manipulation in the wake of the Volkswagen"dieselgate" scandal.