Diferent ETM S60 T5 issues

[Kurica]

Hello,
Got an amazing S60 T5 2002, all great for six monts other then being in limp mode once or twice, while was hot from spring and summer all good, before winter i had headgasket replaced cause some compression leak over 4500 rpm and by the time i finnished the temp had droped and humidity up quiet a bit and my car got this crazy behavior, i goes from 500 rpm to 1500rpm to try to be on idle, when he does that Vida says there are canbus problems, CEM to ECM and ETM conection issues. been arround all canbus wires doing as vida says to find any wire or plug problem, all good. after heat up the engine and wait for a hour or so everything gets normal or in a dry warmer day ( plus 15 ºc), errors disapear and the engine runs great. im thinking it can be the trotle body(since it gets affected by engine heat) or even the ECM for some reason... my question is, how can i accuratly know what is creating this can bus issue, so i dont spend money for parts just for trial and error.

thank in advance!