Alphons Iacobelli pleaded guilty to two charges related to a conspiracy to siphon money from the fund operated jointly by the company and the United Auto Workers union.
Iacobelli will be sentenced May 29 and could face up to 96 months in prison. He pleaded guilty to conspiring to violate the Labor Management Relations Act and for submitting a false tax return.
The former executive was at the center of a multi-year conspiracy investigated by the U.S. Justice Department, which damaged the reputations of Fiat Chrysler Automobiles and the union, which already was struggling to maintain its dominance in the industry, after suffering defeats in efforts to unionize plants in the South.
The government charged four people with siphoning off funds for personal use. In all, officials said more than $1.5 million in worker training funds were diverted over a five-year period ending in 2014, aimed at influencing union officials in favor of the company, according to the plea agreement.
Iacobelli, who from 2008 to 2015 was the company's lead labor negotiator, said he was "acting on behalf of Fiat Chrysler."
He spent money on a second-hand Ferrari, collectible Mont Blanc fountain pens and an extensive list of renovations to his home.
He also admitted he authorized more than $450,000 in credit card charges for jewelry, furniture, electronics and other luxuries for FCA UAW members.
And $262,219 in training center funds were used to pay off the mortgage of former UAW vice president General Holiefield, who died in 2015.
On the tax charge, Iacobelli said he omitted more than $840,000 in income in 2014, obtained illegally through FCA funds.
Copyright Agence France-Presse, 2018