Alfa147

Hi all, im new to the site, but read most of the topics regarding mt problem. I need advise and help please. My engine was recently overhaul but gives me a error code P1758 SV current. Various mechanics and agents struggle to find what the problem is. The gearbox was recalibrate 3 times and still give this error. What could be the problem. This is my first car and i dont want to sell it. I believe this problem could be fix. Please help...many thanks