Hello to everyone, i'm new here , so here is my problem (sorry for my bad english) .

I have an SAAB 9-5 2011 2.0 TiD (123.000 km), and i have a wired problem .
The problem is with automatic transmission. When i drive the car "long time" (about 15/30 minutes, depends on the weather, because when it's hot outside, i drive only 15 minutes, and when it's cold with hot, i drive 30 minutes) until the water temperature increases, the car start's to shake, start's to shocks, and on my board it appears "Transmission Maintenance" and after the engine light problem is illuminated , and after that i can rule only with first gear (i want to mention, i can't change the gear with Manual, doesn't work) . I have this problem after two month's after i buy that car from Italy . The oil from gearbox it's changed (I changed it to a service, so the oil it's ok) and i changed the Valve Block, and after 3,4 months it have similar problem. The tester show me the probleam is : Pressure valve 3, and i changed the Valve Block..wired . I think, the gearbox is not probleam, because i can rule, the gear changed very good, but after 30 minutes (or 15 in other cases) it's appears "Transmission Maintenance" (or i'm wrong about it's not the transmission probleam?) . I don't know what can cause that issue with transmission because i ask so many people, and testing..and nobody knows. So, sorry for my english again if i have mistakes, but i have a major problem , so please help !

Sincerely, Vlad .