At one time there were “easy” ECUs in which it was sufficient to slip out the memory (eprom), read it, modify it, and reinstall it in its housing. Since a few years, ECUs have different types of memory and in most cases all soldered. So the “modus operandi” changes. Desolder, read, modify and re-solder. Many ECUs (as if that were not enough) in addition to having the memory soldered, they also have it glued; drowning it in a bath of glue or resin. So at the time of desoldering and subsequent detachment of the eprom, it might also happen to take some data transmission track with you. Repairing and re-soldering requires not only an excellent gift of patience but also a good hand, and even more so an eagle’s-eye view. But in spite of the eagle’s-eye view, one would still not be sure of having done a safe job.
Here arises the need for a quiet and clean place, possibly not located in mechanics, where grease, grease, dirt and dust almost rule. Of course this room will need to be equipped with soldering irons of different types, viewers at various magnifications, and perhaps even a digital microscope, where the image is directly “shot on the screen” and perhaps even magnified 20 times. Logically we season this with three or four computers, and there we have described our control unit room.