Work on the road was halted last summer pending approval from the audit office.
Now ironed out, work is hoped to be complete by the end of this year.
A ceremony was held in Lagos on Thursday by the concessionaire Rotas do Algarve Litoral to mark the occasion.
In attendance was Minister for Infrastructures Pedro Marques.
However, a date has yet to be announced for the uptake of work on the stretch between Olhão and Vila Real de Santo António, in the Eastern Algarve, which is one of the worst-affected parts of the notorious road.