At the end of 2011, with a firm contract for 2012, the Italian reportedly agreed to vacate his race seat to make room for the well-funded Russian Vitaly Petrov.
But Trulli, now 38, says Fernandes promised to pay him in full for 2012.
Italy's Autosprint says Trulli is angry with Fernandes for not paying him, since the Malaysian entrepreneur has not only increased Caterham's budget, but also that of his English football club Queens Park Rangers.
"I'm going to sue Fernandes," he is quoted as saying, "because he owes me a lot of money.
"My career in formula one ended because I agreed to give up my place, because I was assured that the team would fulfil its contractual obligations.
"To date, this has not occurred," added Trulli, a veteran of over 250 grands prix.