After a recent standard scan it turned out that the error is not related to the mechanics at all, but to the engine control unit. The car started acting weird after a battery drop: the RPMs were unstable, check engine light appeared from time to time. One service even suggested replacing the ECU completely because the firmware might have been corrupted. That’s when I learned how much depends on firmware, EEPROM and different calibration files. I started reading car forums, looking into recovery and backup files for ECU. It turned out that many services, for example ECUFIX, actually search for dumps and firmware in specialized databases, because each model and even each specific ECU number can have different software versions.
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