2007 Toyota Matrix Transmission problem, pressure valve or

My name is Sylwester Flis and I trully need your help. A year ago I move to Poland for a contract brought my 07T. Matrix with me. About two weeks ago first time I noticed that something wasn't right with the tramsmission. While switching gears from 1-2 and 2-3 it gives sudden jerk. From gear 3 to 4 it wasn't as bad. However switching from anything to R-reverse it gave a huge jolt, and that concerned me the most. One thing I missed for about an hour that at the same time "check engine" orange light came on. I went to local Toyota dealer and the guy hooked up his Intelligent Tester and told me that his software is for european cars and it doesn't allow him to check the problem hoever he deleted the "check engine" light. Well, when I left his lot I noticed that removing the light everything worked great. The next morning "check engine" light came back and the transmission problem with it. While looking for another shop the "check engine" light was off for 4 days which I thought the problem resolved it self, but the light came back on and this time for good. I was suggested to go to a mechanic that works on American cars. I went and he hooked up his OBD tester and this code came up: P0748 pressure control solenoid electrical. First he checked the cables, connections and he found nothing suspicious. Light was off for about 10 miles and it came back on. Next he was going to dig to the pressure solenoid valve but he decided to take a final resistance messure at the ecm plug (that's what I saw). After messuring it he got the right ohmage and that ment that the pressure solenoid valve was ok. His decision was that my ECM is at fault. Obviously that news did not make me happy since I already paid him $200 dollars and the car was still not fixed. Here is my question. Do you think this whole story sound right and make sense. And if it is the ECM how much is it and can the computer be fixed. The mechanic said that he may be able to take a look at the ECM but he doesn't have the blue print or the diagram. And he informed me that it may be the problem here in Poland. Please help me anyway you can. I am a wheelchair user on top of as this makes my problem even larger. I appreciate in advance. Sylvester.