All these things have known resistances and waveforms. They can all be diagnosed with a $5 multimeter and $50 scope. Fuel injection became standard closer to

All these things have known resistances and waveforms. They can all be diagnosed with a $5 multimeter and $50 scope. Fuel injection became standard closer to 88. It's not complicated. The systems are pretty tolerant and only need a few sensor to operate (albeit not perfectly). The precision required from various sensors and things is far less than what internet commenters will lead you to believe. Though if someone is gonna build something finicky of course it will be the Germans (requiring software resets when changing basic things is but one example).