Former Fiat Chrysler (FCA) CEO Sergio Marchionne, who played a pivotal role in two corporate turnarounds, has died at the age of 66.

"It is with the deepest sadness that EXOR has learned of the passing of Sergio Marchionne," FCA Chairman John Elkann, from the Agnelli family which has a controlling stake in the auto group, said in a statement Wednesday morning.

“Unfortunately, what we feared has come to pass. Sergio Marchionne, man and friend, is gone. I believe that the best way to honor his memory is to build on the legacy he left us, continuing to develop the human values of responsibility and openness of which he was the most ardent champion."

Marchionne was replaced as CEO of the carmaker last weekend and also stepped down from his dual role as CEO of Ferrari, the race car manufacturer spun off from Fiat more than 2 years ago. The company said at the time that his condition had worsened after he fell gravely ill following complications during surgery in a Zurich hospital.

In an emotional letter at the weekend, Elkann hailed Marchionne's tenure, sought to reassure employees about the future, and rally them around newly appointed CEO Mike Manley.

Tributes from top industry execs poured in throughout Wednesday, with Bill Ford calling Marchionne "one of the most respected leaders in the industry."