u/Low_Laugh7180

Hi everyone. I'm kind of having an issue with my 2009 mazda 6. Two months ago the error code P0302 for a cylinder 2 misfire came up after the car got an oil change. I took it to the mechanic and all four spark plugs were replaced. I drove about 250km and the misfire came back again and the car was running rough. I took it to the mechanic again, he checked the spark plugs again, checked injectors, checked the intake valves and they were all fine. He checked the cables too and everything was fine. He even did a compression test and again everything was fine. He recommended we change the agr valve, i let him do it but i wasn't really sure about that and indeed the error code came up after about 50km. Since everything else seems to be working fine, the mechanic thinks that the ecu might be the problem and the car might need a new one. Is this even possible? If the ecu was the problem wouldn't there be at least 2 or 3 other error codes? Mine shows only P0302. Thanks in advance.