I disagree, I do both, and a modern ECU hardware can be extremely complex .. more so than its software. This is because the hardware needs to meet a stack of c

I disagree, I do both, and a modern ECU hardware can be extremely complex .. more so than its software. This is because the hardware needs to meet a stack of conflicting specifications and standards for EMC, robustness, etc. Things need to work at a wide range of temperatures -40degC to 150degC. Optimising for one standard or parameter causes all your other calibration to go out of whack. Adding a protection element to the circuit can itself fail and be the reason that the circuit fails. At times it can be like the Jenga tower ready to topple over. Modern standards like ISO 26262 make it even more complicated because now we have to calculate and add up the failure probabilities of every single resistor and capacitor to find the whole-circuit failure probability, and in some applications we would need to prove less than 10 FIT (10 per trillion hours). Usually this can’t be reached without adding redundant components, and then maintaining the document trail to explain why they exist and can't be removed. And suppose you need to change a component in the design .. you have to find something to do with the 10,000 units of the old component that you bought a year ago before the design was finished because it was on back order for 100 weeks.