I was driving as normal when the car jolted and then I couldn't get the car out of fourth gear despite slowing down, speeding up, shifting manually, and turning the car off and on. I took it to multiple car mechanics including several Hyundai dealerships, each with various causes of the problem. Hyundai replaced the PCM with no success. They reported that the car needed a new catalytic converter, however we took the car to a muffler shop who told us the catalytic converter was fine. On the way home, the car actually was able to shift as normal and we thought that all would be fine - however, when we got it home and restarted it, it began to have the exact same problem. We took it to a different Hyundai dealer who reported that it was the valve body harness. They said they couldn't do anything else unless the valve body harness was replaced, which cost $540. We replaced this part and it still didn't work. Next they wanted to fix the valve body gasket which they quoted us a cost of $2300. At this point we don't even know what to do, and are considering taking it to yet another mechanic shop because they aren't sure that replacing the valve body gasket will even fix the problem.